In the US, the American College of Obstetricians and Gynecologists suggests healthcare providers consider depression screening for perinatal women. Additionally, the American Academy of Pediatrics recommends pediatricians screen mothers for PPD at 1-month, 2-month and 4-month visits. However, many providers do not consistently provide screening and appropriate follow-up. For example, in Canada, Alberta is the only province with universal PPD screening. This screening is carried out by Public Health nurses with the baby's immunization schedule.

The Edinburgh Postnatal Depression Scale, a standardized self-reported questionnaire, may be used to identify women who have postpartum depression. If the new mother scores 13 or more, she likely has PPD and further assessment should follow.

A 2013 Cochrane review found evidence that psychosocial or psychological intervention after childbirth helped reduce the risk of postnatal depression. These interventions included home visits, telephone-based peer support, and interpersonal psychotherapy. Support is an important aspect of prevention, as depressed mothers commonly state that their feelings of depression were brought on by "lack of support" and "feeling isolated."

In couples, according to a systematic review and meta-analysis of 2015, emotional closeness and global support by the partner protect against both perinatal depression and anxiety. Further factors such as communication between the couple and relationship satisfaction have a protective effect against anxiety alone.

A major part of prevention is being informed about the risk factors. The medical community can play a key role in identifying and treating postpartum depression. Women should be screened by their physician to determine their risk for acquiring postpartum depression. Also, proper exercise and nutrition appear to play a role in preventing postpartum depression and depressed mood in general.

In 2016, the United States Preventive Services Task Force (USPSTF) recommended screening in the adult populations with evidence that it increases the detection of people with depression and with proper treatment improves outcomes. They recommend screening in those between the age of 12 to 18 as well.

A Cochrane review from 2005 found screening programs do not significantly improve detection rates, treatment, or outcome.

A diagnostic assessment may be conducted by a suitably trained general practitioner, or by a psychiatrist or psychologist, who records the person's current circumstances, biographical history, current symptoms, and family history. The broad clinical aim is to formulate the relevant biological, psychological, and social factors that may be impacting on the individual's mood. The assessor may also discuss the person's current ways of regulating mood (healthy or otherwise) such as alcohol and drug use. The assessment also includes a mental state examination, which is an assessment of the person's current mood and thought content, in particular the presence of themes of hopelessness or pessimism, self-harm or suicide, and an absence of positive thoughts or plans. Specialist mental health services are rare in rural areas, and thus diagnosis and management is left largely to primary-care clinicians. This issue is even more marked in developing countries. The mental health examination may include the use of a rating scale such as the Hamilton Rating Scale for Depression or the Beck Depression Inventory or the Suicide Behaviors Questionnaire-Revised. The score on a rating scale alone is insufficient to diagnose depression to the satisfaction of the DSM or ICD, but it provides an indication of the severity of symptoms for a time period, so a person who scores above a given cut-off point can be more thoroughly evaluated for a depressive disorder diagnosis. Several rating scales are used for this purpose.

Primary-care physicians and other non-psychiatrist physicians have more difficulty with underrecognition and undertreatment of depression compared to psychiatric physicians, in part because of the physical symptoms that often accompany depression, in addition to the many potential patient, provider, and system barriers that the authors describe. A review found that non-psychiatrist physicians miss about two-thirds of cases, though this has improved somewhat in more recent studies.

Before diagnosing a major depressive disorder, in general a doctor performs a medical examination and selected investigations to rule out other causes of symptoms. These include blood tests measuring TSH and thyroxine to exclude hypothyroidism; basic electrolytes and serum calcium to rule out a metabolic disturbance; and a full blood count including ESR to rule out a systemic infection or chronic disease. Adverse affective reactions to medications or alcohol misuse are often ruled out, as well. Testosterone levels may be evaluated to diagnose hypogonadism, a cause of depression in men. Vitamin D levels might be evaluated, as low levels of vitamin D have been associated with greater risk for depression.

Subjective cognitive complaints appear in older depressed people, but they can also be indicative of the onset of a dementing disorder, such as Alzheimer's disease. Cognitive testing and brain imaging can help distinguish depression from dementia. A CT scan can exclude brain pathology in those with psychotic, rapid-onset or otherwise unusual symptoms. In general, investigations are not repeated for a subsequent episode unless there is a medical indication.

No biological tests confirm major depression. Biomarkers of depression have been sought to provide an objective method of diagnosis. There are several potential biomarkers, including Brain-Derived Neurotrophic Factor and various functional MRI techniques. One study developed a decision tree model of interpreting a series of fMRI scans taken during various activities. In their subjects, the authors of that study were able to achieve a sensitivity of 80% and a specificity of 87%, corresponding to a negative predictive value of 98% and a positive predictive value of 32% (positive and negative likelihood ratios were 6.15, 0.23, respectively). However, much more research is needed before these tests could be used clinically.

Treatment for Antenatal depression poses many challenges because the baby is also affected by any treatments given to the mother. It is suggested that the emotional aspects are handled first which includes;

- Taking it easy by relaxing when possible.

- Spending time with your partner.

- Talk about your fears & anxieties involving the pregnancy.

- Manage your stress.

Counseling is highly recommended to any woman suffering from antenatal depression. It is a very effective way for the mother to express her feelings and explain in her own words what she is feeling. This is very effective in that it gives the doctors a better insight into the symptoms and their severity. In severe cases Medication can be prescribed. This is usually only done if the symptoms have proven so severe that they interfere with day-to-day life, self care, and ability to sleep. During pregnancy, there are two main kinds of antidepressants used during pregnancy; Tricyclic antidepressants (TCAs)and Selective serotonin reuptake inhibitors (SSRIs).Once prescribed, anti-depressant medication has been found to be extremely effective in treating antenatal depression. Patients can expect to feel an improvement in mood in roughly 2 to 3 weeks on average, and can begin to feel themselves truly connect with their baby. Reported benefits of medication include returned appetite, feeling of connect, increased mood, increased energy, and better concentration. Side effects are minor, though they are reported in some cases. Currently, no abnormalities of the baby have been associated with the use of antidepressants during pregnancy.

It may be true that maternal SSRI use during pregnancy can lead to difficulty for their newborn adjusting to conditions outside of the womb immediately following birth. Some studies indicate that infants with exposure to SSRIs in the second and third trimester were more likely to be admitted to intensive care following their birth for respiratory, cardiac, low weight and other reasons, and that infants with prenatal SSRI exposure exhibited less motor control upon delivery than infants who were not exposed to SSRIs. Newborns who were exposed to SSRIs for five months or more prior to birth were at a greater risk for lower Apgar scores 1 and 5 minutes after delivery, indicating they were of lesser health than newborns who were not exposed to SSRIs before birth. However, prenatal SSRI exposure was not found to have a significant impact the long-term mental and physical health of the children. These results are not independent of any effects of prenatal depression on infants.

Questionnaires and checklists such as the Beck Depression Inventory or the Children's Depression Inventory can be used by a mental health provider to help detect, and assess the severity of depression. The Seasonal Pattern Assessment Questionnaire can be used to screen for seasonal affective disorder. Semi structured interviews such as the Kiddie Schedule for Affective Disorders and Schizophrenia (KSADS) and the Structured Clinical Interview for DSM-IV (SCID) are used for diagnostic confirmation of depression.

For women taking psychiatric medication, the decision as to whether continue during pregnancy and whether to take them while breast feeding is difficult in any case; there is no data to guide this decision with respect to preventing postpartum psychosis. There is no data to guide a decision as to whether women at high risk for postpartum psychosis should take antipsychotic medicine to prevent it. For women at risk of postpartum psychosis, informing medical care-givers, and monitoring by a psychiatrist during pregnancy, in the perinatal period, and for a few weeks following delivery, is recommended.

For women with known bipolar disorder, taking medication during pregnancy roughly halves the risk of a severe postpartum episode, as does starting to take medication immediately after the birth.

Healthcare providers may screen patients for depression using a screening tool, such as the Patient Healthcare Questionnaire-2 (PHQ-2).

To diagnose a major depressive episode, a trained healthcare provider must make sure that:

- The symptoms do not meet the criteria for a mixed episode.

- The symptoms must cause considerable distress or impair functioning at work, in social settings or in other important areas in order to qualify as an episode.

- The symptoms are not due to the direct physiological effects of a substance (e.g., abuse of a drug or medication) or a general medical condition (e.g., hypothyroidism).

- Other than in the case of severe symptoms (severely impaired functioning, severe preoccupation with worthlessness, ideas of suicide, delusions or hallucinations or psychomotor retardation).

Brain imaging (functional/structural MRI) may help direct the search for microscopic abnormalities in brain structure and function responsible for late life depression. Ultimately, imaging technologies may serve as tools for early diagnosis and subtyping of depression.

Though there is no clear-cut way to prevent dysthymia from occurring, some suggestions have been made. Since dysthymia will often first occur in childhood, it is important to identify children who may be at risk. It may be beneficial to work with children in helping to control their stress, increase resilience, boost self-esteem, and provide strong networks of social support. These tactics may be helpful in warding off or delaying dysthymic symptoms.

Antenatal depression affects about one in every eight women. It's becoming more prevalent as more medical studies are being done. Antenatal depression was once thought to simply be the normal stress associated with any pregnancy, and was waved off as a common ailment. It can be caused by many factors, usually though involving aspects of the mothers personal life such as, family, economic standing, relationship status, etc. It can also be caused by hormonal and physical changes that are associated with pregnancy.

Among the psychological assessments for identifying whether or not children and adolescents are experiencing depression and/or depressive symptoms is the Children's Depression Inventory. In early 2016, the USPSTF released an updated recommendation for the screening of adolescents ages 12 to 18 years for major depressive disorder (MDD). Appropriate treatment and follow-up should be provided for adolescents who screen positive.

In most cases hospital admission is necessary. Antipsychotic drugs and mood stabilizing drugs such as lithium are typically administered but is not clear if mood stabilizers can be titrated to a high enough level quickly enough to be effective. Electroconvulsive therapy may be considered, especially if there is a high risk of suicide.

Family support may be provided via a social worker.

Depressed mood may not require professional treatment, and may be a normal temporary reaction to life events, a symptom of some medical condition, or a side effect of some drugs or medical treatments. A prolonged depressed mood, especially in combination with other symptoms, may lead to a diagnosis of a psychiatric or medical condition which may benefit from treatment. Different sub-divisions of depression have different treatment approaches.

In the United States, it has been estimated that two thirds of people with depression do not actively seek treatment. The World Health Organisation (WHO) has predicted that by 2030, depression will account for the highest level of disability accorded any physical or mental disorder in the world (WHO, 2008).

The UK National Institute for Health and Care Excellence (NICE) 2009 guidelines indicate that antidepressants should not be routinely used for the initial treatment of mild depression, because the risk-benefit ratio is poor. A recent meta-analysis also indicated that most antidepressants, besides fluoxetine, do not seem to offer a clear advantage for children and adolescents in the acute treatment of major depressive disorder.

Estimates of the numbers of people suffering from major depressive episodes and Major Depressive Disorder (MDD) vary significantly. In their lifetime, 10% to 25% of women, and 5% to 12% of men will suffer a major depressive episode. Fewer people, between 5% and 9% of women and between 2% and 3% of men, will have MDD, or full-blown depression. The greatest differences in numbers of men and women diagnosed are found in the United States and Europe. The peak period of development is between the ages of 25 and 44 years. Onset of major depressive episodes or MDD often occurs to people in their mid-20s, and less often to those over 65. Prepubescent girls and boys are affected equally. The symptoms of depression are the same in both children and adolescents though there is evidence that their expression within an individual may change as he or she ages.

In a National Institute of Mental Health study, researchers found that more than 40 percent of people with post-traumatic stress disorder suffered from depression 4 months after the traumatic event they experienced.

Cultural factors can influence the symptoms displayed by a person experiencing a major depressive episode. The values of a specific culture may also influence which symptoms are more concerning to the person or and their friends and family. It is essential that a trained professional knows not to dismiss specific symptoms as merely being the "norm" of a culture.

Women who have recently given birth may be at increased risk for having a major depressive episode. This is referred to as postpartum depression and is a different health condition than the baby blues, a low mood that resolves within 10 days after delivery.

The controversy over the use of antidepressants began in 2003 when Great Britain's Department of Health stated that, based on data collected by the Medicines and Healthcare products Regulatory Agency, paroxetine (an antidepressant) should not be used on patients under the age of 18. Since then, the United States Food and Drug Administration (FDA) has issued a warning describing the increased risk of adverse effects of antidepressants used as treatment in those under the age of 18. The main concern is whether the risks outweigh the benefits of the treatment. In order to decide this, studies often look at the adverse effects caused by the medication in comparison to the overall symptom improvement. While multiple studies have shown an improvement or efficacy rate of over 50 percent, the concern of severe side effects – such as suicidal ideation or suicidal attempts, worsening of symptoms, or increase in hostility – are still concerns when using antidepressants. However, an analysis of multiple studies argues that while the risk of suicidal ideation or attempt is present, the benefits significantly outweigh the risks. Due to the variability of these studies, it is currently recommended that if antidepressants are chosen as a method of treatment for children or adolescents, the clinician monitor closely for adverse symptoms, since there is still no definitive answer on the safety and overall efficacy.

The "Diagnostic and Statistical Manual of Mental Disorders IV" (DSM-IV), published by the American Psychiatric Association, characterizes dysthymic disorder. The essential symptom involves the individual feeling depressed for the majority of days, and parts of the day, for at least two years. Low energy, disturbances in sleep or in appetite, and low self-esteem typically contribute to the clinical picture as well. Sufferers have often experienced dysthymia for many years before it is diagnosed. People around them often describe the sufferer in words similar to "just a moody person". Note the following diagnostic criteria:

1. During a majority of days for two years or more, the adult patient reports depressed mood, or appears depressed to others for most of the day.

2. When depressed, the patient has two or more of:

1. decreased or increased appetite

2. decreased or increased sleep (insomnia or hypersomnia)

3. Fatigue or low energy

4. Reduced self-esteem

5. Decreased concentration or problems making decisions

6. Feelings of hopelessness or pessimism

3. During this two-year period, the above symptoms are never absent longer than two consecutive months.

4. During the duration of the two-year period, the patient may have had a perpetual major depressive episode.

5. The patient has not had any manic, hypomanic, or mixed episodes.

6. The patient has never fulfilled criteria for cyclothymic disorder.

7. The depression does not exist only as part of a chronic psychosis (such as schizophrenia or delusional disorder).

8. The symptoms are often not directly caused by a medical illness or by substances, including drug abuse or other medications.

9. The symptoms may cause significant problems or distress in social, work, academic, or other major areas of life functioning.

In children and adolescents, mood can be irritable, and duration must be at least one year, in contrast to two years needed for diagnosis in adults.

Early onset (diagnosis before age 21) is associated with more frequent relapses, psychiatric hospitalizations, and more co-occurring conditions. For younger adults with dysthymia, there is a higher co-occurrence in personality abnormalities and the symptoms are likely chronic. However, in older adults suffering from dysthymia, the psychological symptoms are associated with medical conditions and/or stressful life events and losses.

Dysthymia can be contrasted with major depressive disorder by assessing the acute nature of the symptoms. Dysthymia is far more chronic (long lasting) than major depressive disorder, in which symptoms may be present for as little as 2 weeks. Also Dysthymia often presents itself at an earlier age than Major Depressive Disorder.

Affective disorders in patients with MD can only be detected by means of a clinician-administered diagnostic interview. Organic exclusion rules and other criteria are used in making the diagnosis of MD.

Psychologic therapies are recommended for elderly patients with depression because of this group’s vulnerability to adverse effects and high rates of medical problems and medication use. Psychotherapeutic approaches include cognitive behavioral therapy, supportive psychotherapy, problem-solving therapy, and interpersonal therapy. The potential benefit of psychotherapy is not diminished by increasing age. Older adults often have better treatment compliance, lower dropout rates, and more positive responses to psychotherapy than younger patients. Consultation with a clinical geropsychologist is useful.

According to a substantial amount of epidemiology studies conducted, women are twice as likely to develop certain mood disorders, such as major depression. Although there is an equal number of men and women diagnosed with bipolar II disorder, women have a slightly higher frequency of the disorder.

In 2011, mood disorders were the most common reason for hospitalization among children aged 1–17 years in the United States, with approximately 112,000 stays. Mood disorders were top principal diagnosis for Medicaid super-utilizers in the United States in 2012. Further, a study of 18 States found that mood disorders accounted for the highest number of hospital readmissions among Medicaid patients and the uninsured, with 41,600 Medicaid patients and 12,200 uninsured patients being readmitted within 30 days of their index stay—a readmission rate of 19.8 per 100 admissions and 12.7 per 100 admissions, respectively. In 2012, mood and other behavioral health disorders were the most common diagnoses for Medicaid-covered and uninsured hospital stays in the United States (6.1% of Medicaid stays and 5.2% of uninsured stays).

A study conducted in 1988 to 1994 amongst young American adults involved a selection of demographic and health characteristics. A population-based sample of 8,602 men and women ages 17–39 years participated. Lifetime prevalence were estimated based on six mood measures:

1. major depressive episode (MDE) 8.6%,

2. major depressive disorder with severity (MDE-s) 7.7%,

3. dysthymia 6.2%,

4. MDE-s with dysthymia 3.4%,

5. any bipolar disorder 1.6%, and

6. any mood disorder 11.5%.

The long-term outcome for psychotic depression is generally poorer than for non-psychotic depression.

From the :

F33 Recurrent depressive disorder

- G1.There has been at least one previous episode, mild (F32.0), moderate (F32.1), or severe (F32.2 or F32.3), lasting a minimum of 2 weeks and separated from the current episode by at least 2 months free from any significant mood symptoms.

- G2. At no time in the past has there been an episode meeting the criteria or hypomanic or manic episode (F30.-).

- G3. Most commonly used exclusion criteria: the episode is not attributable to psychoactive substance use (F1) or any organic mental disorder, in the sense of F0. It is recommended to specify the predominant type of previous episodes (mild, moderate, severe, uncertain).

F33.0 Recurrent depressive disorder, current episode mild

- A. The general criteria for recurrent depressive disorder (F33) are met.

- B. The current episode meets the criteria for depressive episode, mild severity (F32.0).

- A fifth character may be used to specify the presence of the somatic syndrome, as defined in F32, in the current episode:

- F33.00 without somatic syndrome

- F33.01 with somatic syndrome

F33.1 Recurrent depressive disorder, current episode moderate

- A. The general criteria for recurrent depressive disorders (F33) are met.

- B. The current episode meets the criteria for depressive episode, moderate severity (F32.1).

- A fifth character may be used to specify the presence of the somatic syndrome, as defined in F32, in the current episode:

F33.10 without somatic syndrome

F33.11 with somatic syndrome

F33.2 Recurrent depressive disorder, current episode severe without psychotic symptoms

- A. The general criteria for recurrent depressive disorders (F33) are met.

- B. The current episode meets the criteria for severe depressive episode without psychotic symptoms (F32.2).

F33.3 Recurrent depressive disorder, current episode severe with psychotic symptoms

- A. The general criteria for recurrent depressive disorders (F33) are met.

- B. The current episode meets the criteria for severe depressive episode with psychotic symptoms (F32.3). A fifth character may be used to specify whether the psychotic symptoms are congruent or incongruent with the mood:

F33.30 with mood congruent psychotic symptoms

F33.31 with mood incongruent psychotic symptoms

F33.4 Recurrent depressive disorder, currently in remission

- A. The general criteria for recurrent depressive disorder (F33) have been met in the past.

- B. The current state does not meet the criteria for a depressive episode (F32.-) of any severity, or for any other disorder in F3 (the patient may receive treatment to reduce the risk of further episodes).

F33.8 Other recurrent depressive disorders

F33.9 Recurrent depressive disorder, unspecified

Treatment-resistant depression is associated with more instances of relapse than depression that is responsive to treatment. One study showed that as many as 80% of patients who needed more than one course of treatment relapsed within a year. Treatment-resistant depression has also been associated with lower long term quality of life.

Individuals suffering from endogenous depression require treatment plans that focus on the internal, cognitive thought processes since internal stressors are the root of somatic symptoms. Individual cognitive therapy (ICT) is therefore a common treatment used to gain insight to the individual's internal conflicts or thoughts that are motivating their distressing symptoms. Once the cause of the symptoms are identified, sessions are used to develop new coping skills, behavior modification, and changes in beliefs.

As preventative measures, pharmaceuticals such as SSRI's and antidepressants may also be utilized to avoid further development or progression to Major Depressive Disorder. There have been few treatments targeted specifically toward Endogenous Depression; therefore, symptoms are often managed similarly to Major Depressive Disorder. One such treatment is electroconvulsive therapy (ECT). ECT is used as a treatment option for endogenous depression in adults, however, practitioners avoid the use of ECT in young adolescents due to rates of injury.

The DSM-5, released in May 2013, separates the mood disorder chapter from the DSM-TR-IV into two sections: Depressive and Related Disorders and Bipolar and Related Disorders. Bipolar Disorders falls in between Depressive Disorders and Schizophrenia Spectrum and Related Disorders “in recognition of their place as a bridge between the two diagnostic classes in terms of symptomatology, family history and genetics” (Ref. 1, p 123). Bipolar Disorders underwent a few changes in the DSM-5, most notably the addition of more specific symptomology related to hypomanic and mixed manic states. Depressive Disorders underwent the most changes, the addition of three new disorders: disruptive mood dysregulation disorder, persistent depressive disorder (previously dysthymia), and premenstrual dysphoric disorder (previously in Appendix B, the section for disorders needing further research). Disruptive mood dysregulation disorder is meant as a diagnosis for children and adolescents who would normally be diagnosed with bipolar disorder as a way to limit the bipolar diagnosis in this age cohort. Major depressive disorder (MDD) also underwent a notable change, in that the bereavement clause has been removed. Those previously exempt from a diagnosis of MDD due to bereavement are now candidates for the MDD diagnosis.