As with other anxiety disorders, children with SAD face more obstacles at school than those without anxiety disorders. Adjustment and relating school functioning have been found to be much more difficult for anxious children. In some severe forms of SAD, children may act disruptively in class or may refuse to attend school altogether. It is estimated that nearly 75% of children with SAD exhibit some form of school refusal behavior.

This is a serious problem because, as children fall further behind in coursework, it becomes increasingly difficult for them to return to school.

Short-term problems resulting from academic refusal include poor academic performance or decline in performance, alienation from peers, and conflict within the family.

Although school refusal behavior is common among children with SAD, it is important to note that school refusal behavior is sometimes linked to generalized anxiety disorder or possibly a mood disorder. That being said, a majority of children with separation anxiety disorder have school refusal as a symptom. Up to 80% of children who refuse school qualify for a diagnosis of separation anxiety disorder.

The single largest category of anxiety disorders is that of specific phobias which includes all cases in which fear and anxiety are triggered by a specific stimulus or situation. Between 5% and 12% of the population worldwide suffer from specific phobias. Sufferers typically anticipate terrifying consequences from encountering the object of their fear, which can be anything from an animal to a location to a bodily fluid to a particular situation. Common phobias are flying, blood, water, highway driving, and tunnels. When people are exposed to their phobia, they may experience trembling, shortness of breath, or rapid heartbeat. People understand that their fear is not proportional to the actual potential danger but still are overwhelmed by it.

With panic disorder, a person has brief attacks of intense terror and apprehension, often marked by trembling, shaking, confusion, dizziness, nausea, and/or difficulty breathing. These panic attacks, defined by the APA as fear or discomfort that abruptly arises and peaks in less than ten minutes, can last for several hours. Attacks can be triggered by stress, fear, or even exercise; the specific cause is not always apparent.

In addition to recurrent unexpected panic attacks, a diagnosis of panic disorder requires that said attacks have chronic consequences: either worry over the attacks' potential implications, persistent fear of future attacks, or significant changes in behavior related to the attacks. As such, those suffering from panic disorder experience symptoms even outside specific panic episodes. Often, normal changes in heartbeat are noticed by a panic sufferer, leading them to think something is wrong with their heart or they are about to have another panic attack. In some cases, a heightened awareness (hypervigilance) of body functioning occurs during panic attacks, wherein any perceived physiological change is interpreted as a possible life-threatening illness (i.e., extreme hypochondriasis).

In cognitive models of social anxiety disorder, those with social phobias experience dread over how they will be presented to others. They may feel overly self-conscious, pay high self-attention after the activity, or have high performance standards for themselves. According to the social psychology theory of self-presentation, a sufferer attempts to create a well-mannered impression towards others but believes he or she is unable to do so. Many times, prior to the potentially anxiety-provoking social situation, sufferers may deliberately review what could go wrong and how to deal with each unexpected case. After the event, they may have the perception that they performed unsatisfactorily. Consequently, they will perceive anything that may have possibly been abnormal as embarrassing. These thoughts may extend for weeks or longer. Cognitive distortions are a hallmark, and are learned about in CBT (cognitive-behavioral therapy). Thoughts are often self-defeating and inaccurate. Those with social phobia tend to interpret neutral or ambiguous conversations with a negative outlook, and many studies suggest that socially anxious individuals remember more negative memories than those less distressed.

An example of an instance may be that of an employee presenting to their co-workers. During the presentation, the person may stutter a word, upon which he or she may worry that other people significantly noticed and think that their perceptions of him or her as a presenter have been tarnished. This cognitive thought propels further anxiety which compounds with further stuttering, sweating, and, potentially, a panic attack.

Social anxiety disorder (SAD), also known as social phobia, is an anxiety disorder characterized by a significant amount of fear in one or more social situations, causing considerable distress and impaired ability to function in at least some parts of daily life. These fears can be triggered by perceived or actual scrutiny from others.

Physical symptoms often include excessive blushing, excess sweating, trembling, palpitations, and nausea. Stammering may be present, along with rapid speech. Panic attacks can also occur under intense fear and discomfort. Some sufferers may use alcohol or other drugs to reduce fears and inhibitions at social events. It is common for sufferers of social phobia to self-medicate in this fashion, especially if they are undiagnosed, untreated, or both; this can lead to alcoholism, eating disorders or other kinds of substance abuse. SAD is sometimes referred to as an "illness of lost opportunities" where "individuals make major life choices to accommodate their illness". According to ICD-10 guidelines, the main diagnostic criteria of social phobia are fear of being the focus of attention, or fear of behaving in a way that will be embarrassing or humiliating, avoidance and anxiety symptoms. Standardized rating scales can be used to screen for social anxiety disorder and measure the severity of anxiety.

The first line treatment for social anxiety disorder is cognitive behavioral therapy (CBT) with medications recommended only in those who are not interested in therapy. CBT is effective in treating social phobia, whether delivered individually or in a group setting. The cognitive and behavioral components seek to change thought patterns and physical reactions to anxiety-inducing situations. The attention given to social anxiety disorder has significantly increased since 1999 with the approval and marketing of drugs for its treatment. Prescribed medications include several classes of antidepressants: selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), and monoamine oxidase inhibitors (MAOIs). Other commonly used medications include beta blockers and benzodiazepines. It is the most common anxiety disorder with up to 10% of people being affected at some point in their life.

Just how SAD affects a child's attendance and participation in school, their avoidance behaviors stay with them as they grow and enter adulthood. Recently, "the effects of mental illness on workplace productivity have become a prominent concern on both the national and international fronts". In general, mental illness is a common health problem among working adults, 20 to 30% of adults will suffer from at least one psychiatric disorder. Mental illness is linked to decreased productivity, and with individuals diagnosed with SAD their levels at which they function decreases dramatically resulting in partial work-days, increase in number of total absences, and "holding back" when it comes to carrying out and completing tasks.

Premenstrual dysphoric disorder (PMDD) is a severe form of premenstrual syndrome (PMS). Like PMS, premenstrual dysphoric disorder follows a predictable, cyclic pattern. Symptoms begin in the late luteal phase of the menstrual cycle (after ovulation) and end shortly after menstruation begins. On average, the symptoms last six days but can start up to two weeks before menses. The most intense symptoms occur two days before the start of menstrual blood flow through the first day of menstrual blood flow. The symptoms should cease shortly after the start of the menstrual period.

The symptoms in PMDD can be both physical and emotional with mood symptom being dominant. The most debilitating symptoms are emotional and include "irritability, depression, mood lability, anxiety, feelings of ‘loss of control’, difficulty concentrating and fatigue." The physical symptoms include "abdominal bloating, breast tenderness, headache and generalized aches."

Dysthymia, now known as persistent depressive disorder (PDD), is a mood disorder consisting of the same cognitive and physical problems as depression, with less severe but longer-lasting symptoms. The concept was coined by Robert Spitzer as a replacement for the term "depressive personality" in the late 1970s.

According to the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders, published in 1994 (DSM-IV), dysthymia is a serious state of chronic depression, which persists for at least two years (one year for children and adolescents). Dysthymia is less acute and severe than major depressive disorder. As dysthymia is a chronic disorder, sufferers may experience symptoms for many years before it is diagnosed, if diagnosis occurs at all. As a result, they may believe that depression is a part of their character, so they may not even discuss their symptoms with doctors, family members or friends.

Dysthymia often co-occurs with other mental disorders. A "double depression" is the occurrence of episodes of major depression in addition to dysthymia. Switching between periods of dysthymic moods and periods of hypomanic moods is indicative of cyclothymia, which is a mild variant of bipolar disorder.

In the DSM-5, dysthymia is replaced by persistent depressive disorder. This new condition includes both chronic major depressive disorder and the previous dysthymic disorder. The reason for this change is that there was no evidence for meaningful differences between these two conditions.

The term is from Ancient Greek , meaning bad state of mind.

Authoritative diagnostic criteria for PMDD are provided by a number of expert medical guides, notably the Diagnostic and Statistical Manual of Mental Disorders 5 (DSM-5). The "Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5)," established seven criteria (A through G) for the diagnosis of PMDD.

Diagnostic Criteria:

Criterion A is that in most menstrual cycles during the past year, at least 5 of the following 11 symptoms (including at least 1 of the first 4 listed) must be present in the final week before the onset of menses, start to improve within a few days after the onset of menses, and become minimal or absent in the week postmenses.

1. Marked lability (e.g., mood swings)

2. Marked irritability or anger

3. Markedly depressed mood

4. Marked anxiety and tension

5. Decreased interest in usual activities

6. Difficulty in concentration

7. Lethargy and marked lack of energy

8. Marked change in appetite (e.g., overeating or specific food cravings)

9. Hypersomnia or insomnia

10. Feeling overwhelmed or out of control

11. Physical symptoms (e.g., breast tenderness or swelling, joint or muscle pain, a sensation of ‘bloating’ and weight gain)

Criterion B one (or more) of the following symptoms must be present:

1. Marked affective lability (e.g., mood swings; feeling suddenly sad or tearful, or increased sensitivity to rejection).

2. Marked irritability or anger or increased interpersonal conflicts.

3. Marked depressed mood, feelings of hopelessness, or self-deprecating thoughts.

4. Marked anxiety, tension, and/or feelings of being keyed up or on edge.

Criterion C one (or more) of the following symptoms must be present additionally, to reach a total of "five" symptoms when combined with symptoms from Criterion B above.

1. Decreased interest in usual activities (e.g., work, school, friends, hobbies).

2. Subjective difficulty in concentration.

3. Lethargy, easy fatigability, or marked lack of energy.

4. Marked change in appetite; overeating; or specific food cravings.

5. Hypersomnia or insomnia.

6. A sense of being overwhelmed or out of control.

7. Physical symptoms such as breast tenderness or swelling, joint or muscle pain, a sensation of "bloating," or weight gain.

Note: The symptoms in Criteria A-C must have been met for most menstrual cycles that occurred in the preceding year.

Criterion D The symptoms are associated with clinically significant distress or interference with work, school, usual social activities, or relationships with others (e.g., avoidance of social activities; decreased productivity and efficiency at work, school, or home).

Criterion E The disturbance is not merely an exacerbation of the symptoms of another disorder, such as major depressive disorder, panic disorder, persistent depressive disorder (dysthymia), or a personality disorder (although it may co-occur with any of these disorders).

Criterion F Criterion A should be confirmed by prospective daily ratings during at least two symptomatic cycles. (Note: The diagnosis may be made provisionally prior to this confirmation.)

Criterion G The symptoms are not attributable to the physiological effects of a substance (e.g., a drug of abuse, a medication, other treatment) or another medical condition (e.g., hyperthyroidism).

According to the DSM-5, a diagnosis of PMDD requires the presence of at least five of these symptoms with one of the symptoms being number 1-4 (marked lability, irritability, depressed mood, anxiety and tension). These symptoms should occur during the week before menses and remit after initiation of menses. In order to meet criteria for the diagnosis, the symptoms should be charted prospectively for two consecutive ovulation cycles in order to confirm temporal and cyclical nature of symptoms. The symptoms should also be severe enough to affect normal work, school, or social activities or relationships with others.

Other organizations that have published diagnostic criteria for PMDD include the American College of Obstetricians and Gynecologists, the Royal College of Obstetricians and Gynecologists, and the International Society for the Study of Premenstrual Disorders (ISPMD). The ISPMD was a consensus group established by an international multidisciplinary group of experts. The group's diagnostic criteria for PMDD focuses on the cyclic nature of the symptom occurring during the luteal phase of the menstrual cycle, symptoms being absent after menstruation and before ovulation and causing significant impairment. The ISPMD diagnostic criteria for PMDD do not specify symptom characteristics or number of symptoms.

Diagnostic criteria for PMDD are also provided by the 2016 World Health Organization's International Classification of Diseases (ICD-10-CM):

Premenstrual tension syndrome

A more severe and disabling form of premenstrual syndrome in which mood symptoms are the primary characteristic.

A term used to describe the psychological aspects of premenstrual syndrome, such as the "indescribable tension", depression, hostility, and increased seizure activity in people with seizure disorder.

Applicable To

Premenstrual dysphoric disorder ...

Thus today many well-recognized health organizations in many parts of the world provide guides for the diagnosis of PMDD. As a historical footnote, early drafts of the ICD failed to recognize PMDD as a separate condition. In 2003, before the current ICD 10 guidelines, the Committee for Proprietary Medicinal Products required the manufacturer of Prozac (fluoxetine) to remove PMDD from the list of indications for fluoxetine sold in Europe. Reflecting an earlier approach by the ICD, the committee found in 2003 that PMDD was not a well-established disease entity across Europe, and noted "considerable concern that [people] with less severe pre-menstrual symptoms might erroneously receive a diagnosis of PMDD resulting in widespread inappropriate short and long-term use of fluoxetine."

In Australia, PMDD is recognized by the Therapeutic Goods Administration. However, SSRIs are not reimbursed for PMDD under the Pharmaceutical Benefits Scheme.

Dysthymia characteristics include an extended period of depressed mood combined with at least two other symptoms which may include insomnia or hypersomnia, fatigue or low energy, eating changes (more or less), low self-esteem, or feelings of hopelessness. Poor concentration or difficulty making decisions are treated as another possible symptom. Mild degrees of dysthymia may result in people withdrawing from stress and avoiding opportunities for failure. In more severe cases of dysthymia, people may even withdraw from daily activities. They will usually find little pleasure in usual activities and pastimes. Diagnosis of dysthymia can be difficult because of the subtle nature of the symptoms and patients can often hide them in social situations, making it challenging for others to detect symptoms. Additionally, dysthymia often occurs at the same time as other psychological disorders, which adds a level of complexity in determining the presence of dysthymia, particularly because there is often an overlap in the symptoms of disorders. There is a high incidence of comorbid illness in those with dysthymia. Suicidal behavior is also a particular problem with persons with dysthymia. It is vital to look for signs of major depression, panic disorder, generalised anxiety disorder, alcohol and substance misuse and personality disorder.

SAD is a type of major depressive disorder, and sufferers may exhibit any of the associated symptoms, such as feelings of hopelessness and worthlessness, thoughts of suicide, loss of interest in activities, withdrawal from social interaction, sleep and appetite problems, difficulty with concentrating and making decisions, decreased sex drive, a lack of energy, or agitation. Symptoms of winter SAD often include oversleeping or difficulty waking up in the morning, nausea, and a tendency to over eat, often with a craving for carbohydrates, which leads to weight gain. SAD is typically associated with winter depression, but springtime lethargy or other seasonal mood patterns are not uncommon. Although each individual case is different, in contrast to winter SAD, people who experience spring and summer depression may be more likely to show symptoms such as insomnia, decreased appetite and weight loss, and agitation or anxiety.

Seasonal affective disorder (SAD) is a mood disorder subset in which people who have normal mental health throughout most of the year exhibit depressive symptoms at the same time each year, most commonly in the winter. People may sleep too much or have little energy. The condition in the summer can include heightened anxiety.

In the "Diagnostic and Statistical Manual of Mental Disorders" DSM-IV and DSM-5, its status was changed. It is no longer classified as a unique mood disorder but is now a specifier, called "with seasonal pattern", for recurrent major depressive disorder that occurs at a specific time of the year and fully remits otherwise. Although experts were initially skeptical, this condition is now recognized as a common disorder. SAD's highlighting of the disparity in people's moods at different points in the year, and the differing climates in which these discrepancies are measured, therefore advocates the importance of perceiving climate change as an immediate threat to people's mental health, both psychologically and psycho-socially.

SAD in the United States affects from 1.4% in Florida to 9.9% in Alaska. SAD was formally described and named in 1984 by Norman E. Rosenthal and colleagues at the National Institute of Mental Health. The validity of SAD has been questioned by a 2016 analysis by the Center for Disease Control, in which no links were detected between depression and seasonality or sunlight exposure.

Depression is a state of low mood and aversion to activity. It may be a normal reaction to occurring life events or circumstances, a symptom of a medical condition, a side effect of drugs or medical treatments, or a symptom of certain psychiatric syndromes, such as the mood disorders major depressive disorder and dysthymia. Depression in childhood and adolescence is similar to adult major depressive disorder, although young sufferers may exhibit increased irritability or aggressive and self-destructive behavior, rather than the all-encompassing sadness associated with adult forms of depression. Children who are under stress, experience loss, or have attention, learning, behavioral, or anxiety disorders are at a higher risk for depression. Childhood depression is often co-morbid with mental disorders outside of other mood disorders; most commonly anxiety disorder and conduct disorder. Depression also tends to run in families. Psychologists have developed different treatments to assist children and adolescents suffering from depression, though the legitimacy of the diagnosis of childhood depression as a psychiatric disorder, as well as the efficacy of various methods of assessment and treatment, remains controversial.

Minor depressive disorder is very similar to major depressive disorder in the symptoms present. Generally, a person's mood is affected by thoughts and feelings of being sad or down on themself or by a loss of interest in nearly all activities. People can experience ups and downs in their life everyday where an event, action, stress or many other factors can affect their feelings on that day. However, depression occurs when those feelings of sadness persist for longer than a few weeks.

A person is considered to have minor depressive disorder if they experience 2 to 4 depressive symptoms during a 2-week period. The Diagnostic and Statistical Manual of Mental Disorders lists the major depressive symptoms. Depressed mood most of the day and/or loss of interest or pleasure in normal activities must be experienced by the individual to be considered to have minor depressive disorder. Without either of these two symptoms, the disorder is not classified as minor depressive disorder. Other depressive symptoms include significant weight loss or weight gain without trying to diet (an increase/decrease in appetite can provide clues as well), insomnia or hypersomnia, psychomotor agitation or psychomotor retardation, fatigue or loss of energy, and feelings of worthlessness or excessive guilt.

All of these signs can compound on each other to create the last major symptom group of minor depressive disorder: thoughts of death, suicidal thoughts, plans to commit suicide, or a suicide attempt.

Minor depressive disorder differs from major depressive disorder in the number of symptoms present with 5 or more symptoms necessary for a diagnosis of major depressive disorder. Both disorders require either depressed mood or loss of interest or pleasure in normal activities to be one of the symptoms and the symptoms need to be present for two weeks or longer. Symptoms also must be present for the majority of the length of a day and present for a majority of the days in the two-week period. Diagnosis can only occur if the symptoms cause "clinically significant distress or impairment". Dysthymia consists of the same depressive symptoms, but its main differentiable feature is its longer-lasting nature as compared to minor depressive disorder. Dysthymia was replaced in the DSM-5 by persistent depressive disorder, which combined dysthymia with chronic major depressive disorder.

Minor depressive disorder, also known as minor depression, is a mood disorder that does not meet the full criteria for major depressive disorder but at least two depressive symptoms are present for two weeks. These symptoms can be seen in many different psychiatric and mental disorders, which can lead to more specific diagnoses of an individual's condition. However, some of the situations might not fall under specific categories listed in the "Diagnostic and Statistical Manual of Mental Disorders". Minor depressive disorder is an example of one of these nonspecific diagnoses, as it is a disorder classified in the DSM-IV-TR under the category Depressive Disorder Not Otherwise Specified (DD-NOS). The classification of NOS depressive disorders is up for debate. Minor depressive disorder as a term was never an officially accepted term, but was listed in Appendix B of the DSM-IV-TR. This is the only version of the DSM that contains the term, as the prior versions and the most recent edition, DSM-5, does not mention it.

A person is considered to have minor depressive disorder if they experience 2 to 4 depressive symptoms, with one of them being either depressed mood or loss of interest or pleasure, during a 2-week period. The person must not have experienced the symptoms for 2 years and there must not have been one specific event that caused the symptoms to arise. Although not all cases of minor depressive disorder are deemed in need of treatment, some cases are treated similarly to major depressive disorder. This treatment includes cognitive behavioral therapy (CBT), anti-depressant medication, and combination therapy. A lot of research supports the notion that minor depressive disorder is an early stage of major depressive disorder, or that it is simply highly predictive of subsequent major depressive disorder.

The criteria below are based on the formal DSM-IV criteria for a major depressive episode. A diagnosis of major depressive episode requires that the patient has—over a two-week period—experienced five or more of the symptoms below, and these must be outside the patient's normal behaviour. Either depressed mood or decreased interest or pleasure must be one of the five (although both are frequently present).

A person experiencing a depressive episode may have a marked loss or gain of weight (such as 5% of their body weight in one month) or a change in appetite.

Changes in appetite take on two manifestations: under- or over-eating.

In the first instance, some people never feel hungry, can go long periods without wanting to eat, or may forget to eat; if they do eat, a small amount of food may be sufficient. In children, failure to make expected weight gains may be counted towards this criteria. Under-eating is often associated with a melancholic type of depression.

In the second instance, some people tend toward an increase in appetite and may gain significant amounts of weight. They may crave certain types of food, such as sweets or carbohydrates. People with seasonal affective disorder (SAD) often crave foods high in carbohydrates. Over-eating is often associated with a type of depression called atypical depression.

According to the DSM-IV, children must exhibit either a depressed mood or a loss of interest or pleasure in normal activities. These activities may include school, extracurricular activities, or peer interactions. Depressive moods in children can be expressed as being unusually irritable, which may be displayed by "acting out," behaving recklessly, or often reacting with anger or hostility. Children who do not have the cognitive or language development to properly express mood states can also exhibit their mood through physical complaints such as showing sad facial expressions (frowning) and poor eye contact. A child must also exhibit four other symptoms in order to be clinically diagnosed. However, according to the Omnigraphics "Health References Series: Depression Sourcebook, Third Edition", a more calculated evaluation must be given by a medical or mental health professional such as a physiologist or psychiatrist. Following the bases of symptoms, signs include, but are not limited to, an unusual change in sleep habits (for example, trouble sleeping or overly indulged sleeping hours); a significant amount of weight gain/loss by lack or excessive eating; experiencing aches/pains for no apparent reason that can found; and an inability to concentrate on tasks or activities. If these symptoms are present for a period of two weeks or longer, it is safe to make the assumption that the child, or anybody else for that matter, is falling into major depression.

Major depression significantly affects a person's family and personal relationships, work or school life, sleeping and eating habits, and general health. Its impact on functioning and well-being has been compared to that of other chronic medical conditions such as diabetes.

A person having a major depressive episode usually exhibits a very low mood, which pervades all aspects of life, and an inability to experience pleasure in activities that were formerly enjoyed. Depressed people may be preoccupied with, or ruminate over, thoughts and feelings of worthlessness, inappropriate guilt or regret, helplessness, hopelessness, and self-hatred. In severe cases, depressed people may have symptoms of psychosis. These symptoms include delusions or, less commonly, hallucinations, usually unpleasant. Other symptoms of depression include poor concentration and memory (especially in those with melancholic or psychotic features), withdrawal from social situations and activities, reduced sex drive, irritability, and thoughts of death or suicide. Insomnia is common among the depressed. In the typical pattern, a person wakes very early and cannot get back to sleep. Hypersomnia, or oversleeping, can also happen. Some antidepressants may also cause insomnia due to their stimulating effect.

A depressed person may report multiple physical symptoms such as fatigue, headaches, or digestive problems; physical complaints are the most common presenting problem in developing countries, according to the World Health Organization's criteria for depression. Appetite often decreases, with resulting weight loss, although increased appetite and weight gain occasionally occur. Family and friends may notice that the person's behavior is either agitated or lethargic. Older depressed people may have cognitive symptoms of recent onset, such as forgetfulness, and a more noticeable slowing of movements. Depression often coexists with physical disorders common among the elderly, such as stroke, other cardiovascular diseases, Parkinson's disease, and chronic obstructive pulmonary disease.

Depressed children may often display an irritable mood rather than a depressed mood, and show varying symptoms depending on age and situation. Most lose interest in school and show a decline in academic performance. They may be described as clingy, demanding, dependent, or insecure. Diagnosis may be delayed or missed when symptoms are interpreted as normal moodiness.

Physical symptoms include:

- palpitations

- anorexia

- dry mouth

- insomnia

- thoracic/chest pressure

- respiratory difficulties

- epigastric mass

- headache

- a whole-body sensation of heat (distinct from heat intolerance, a symptom of hyperthyroidism)

Psychological symptoms include:

- being easily startled

- externalization of anger, also known in Korean as "bun" (분, 憤, "eruption of anger"), a Korean culture-related sentiment related to social unfairness

- generally sad mood

- frequent sighing

- a feeling of "eok-ul" (억울, 抑鬱, [feeling of] unfairness)

- being easily agitated

- feelings of guilt

- feelings of impending doom

Diagnosed patients may also have a medical history of prior major depressive disorder, dysthymic disorder, anxiety disorders, somatoform disorders, or adjustment disorder according to the "Diagnostic and Statistical Manual of Mental Disorders", fourth edition (DSM-IV) criteria.

Diagnosed patients are most likely to be middle-aged, post-menopausal women with low socio-economic status.

Major depression frequently co-occurs with other psychiatric problems. The 1990–92 "National Comorbidity Survey" (US) reports that half of those with major depression also have lifetime anxiety and its associated disorders such as generalized anxiety disorder. Anxiety symptoms can have a major impact on the course of a depressive illness, with delayed recovery, increased risk of relapse, greater disability and increased suicide attempts. There are increased rates of alcohol and drug abuse and particularly dependence, and around a third of individuals diagnosed with ADHD develop comorbid depression. Post-traumatic stress disorder and depression often co-occur. Depression may also coexist with attention deficit hyperactivity disorder (ADHD), complicating the diagnosis and treatment of both. Depression is also frequently comorbid with alcohol abuse and personality disorders.

Depression and pain often co-occur. One or more pain symptoms are present in 65% of depressed patients, and anywhere from 5 to 85% of patients with pain will be suffering from depression, depending on the setting; there is a lower prevalence in general practice, and higher in specialty clinics. The diagnosis of depression is often delayed or missed, and the outcome can worsen if the depression is noticed but completely misunderstood.

Depression is also associated with a 1.5- to 2-fold increased risk of cardiovascular disease, independent of other known risk factors, and is itself linked directly or indirectly to risk factors such as smoking and obesity. People with major depression are less likely to follow medical recommendations for treating and preventing cardiovascular disorders, which further increases their risk of medical complications. In addition, cardiologists may not recognize underlying depression that complicates a cardiovascular problem under their care.

It is during depressive episodes that BP-II patients often seek help. Symptoms may be syndromal or subsyndromal. Depressive BP-II symptoms may include five or more of the below symptoms (at least one of them must be either depressed mood or loss of interest/pleasure). In order to be diagnosed, they need to be present only during the same two-week period, as a change from previous hypomanic functioning:

- Depressed mood most of the day, nearly every day, as indicated by either subjective report (e.g., feels sad, empty, or hopeless) or observation made by others (e.g., appears tearful). (Note: In children and adolescents, can be irritable mood.)

- Markedly diminished interest or pleasure in all, or almost all, activities most of the day, nearly every day (as indicated by either subjective account or observation).

- Significant weight loss when not dieting or weight gain (e.g., a change of more than 5% of body weight in a month), or decrease or increase in appetite nearly every day. (Note: In children, consider failure to make expected weight gain.)

- Insomnia or hypersomnia nearly every day.

- Psychomotor agitation or retardation nearly every day (observable by others; not merely subjective feelings of restlessness or being slowed down).

- Fatigue or loss of energy nearly every day.

- Feelings of worthlessness or excessive or inappropriate guilt nearly every day (not merely self-reproach or guilt about being sick).

- Diminished ability to think or concentrate, possible irritability or indecisiveness, nearly every day (either by subjective account or as observed by others).

- Recurrent thoughts of death (not just fear of dying), recurrent suicidal ideation without a specific plan, a suicide attempt, or a specific plan for committing suicide.

Evidence also suggests that BP-II is strongly associated with atypical depression. Essentially, this means that many BP-II patients exhibit reverse vegetative symptoms. BP-II patients may have a tendency to oversleep and overeat, while typically depressed patients sleep and eat less than usual.

Depressive mixed states occur when patients experience depression and non-euphoric, usually subsyndromal, hypomania at the same time. As mentioned previously, it is particularly difficult to diagnose BP-II when a patient is in this state.

In a mixed state, mood is depressed, but the following symptoms of hypomania present as well:

- Irritability

- Mental overactivity

- Behavioral overactivity

Mixed states are associated with greater levels of suicidality than non-mixed depression. Antidepressants may increase this risk.

Experts describe the spectrum of behaviors designated as addictive in terms of five interrelated concepts: patterns, habits, compulsions, impulse control disorders, and physical addiction.

Psychiatric co-morbidity in ORS is reported. Depression, which is often severe, may be a result of ORS, or may be pre-existing. Personality disorders, especially cluster C, and predominantly the avoidant type, may exist with ORS. bipolar disorder, schizophrenia, hypochondriasis, alcohol, drug abuse and obsessive compulsive disorder.