Symptoms of PTSD generally begin within the first 3 months after the inciting traumatic event, but may not begin until years later. In the typical case, the individual with PTSD persistently avoids trauma-related thoughts and emotions, and discussion of the traumatic event, and may even have amnesia of the event. However, the event is commonly relived by the individual through intrusive, recurrent recollections, flashbacks, and nightmares. While it is common to have symptoms after any traumatic event, these must persist to a sufficient degree (i.e., causing dysfunction in life or clinical levels of distress) for longer than one month after the trauma to be classified as PTSD (clinically significant dysfunction or distress for less than one month after the trauma may be acute stress disorder).

The "DSM-IV" specifies that ASD must be accompanied by the presence of dissociative symptoms, which largely differentiates it from PTSD.

Dissociative symptoms include a sense of numbing or detachment from emotional reactions, a sense of physical detachment, such as seeing oneself from another perspective, decreased awareness of one’s surroundings, the perception that one’s environment is unreal or dreamlike, and the inability to recall critical aspects of the traumatic event (dissociative amnesia).

In addition to the characteristic dissociative symptoms, ASD shares many of the symptoms with PTSD, including:

- the experience or witnessing of a threatening event that resulted in intense fear or horror

- the re-experiencing of the event by means of flashbacks, recurrent thoughts or dreams, and distress when reminded of the event

- the avoidance of stimuli that serve as reminders of the event, such as feelings, thoughts, places, individuals, and activities

- anxiety, including restlessness, difficulty sleeping and concentrating, and hypervigilance

- a significant disruption in normal social or work functioning

The term ASR was first used to describe the symptoms of soldiers during World War I and II, and it was therefore also termed combat stress reaction (CSR). Approximately 20% of U.S. troops displayed symptoms of CSR during WWII, and it was assumed to be a temporary response of healthy individuals to witnessing or experiencing traumatic events. Symptoms include depression, anxiety, withdrawal, confusion, paranoia and sympathetic hyperactivity.

The APA officially included the term ASD in the "DSM-IV" in 1994, and prior to that, symptomatic individuals within the first month of trauma were diagnosed with adjustment disorder. According to the "DSM IV", ASR refers to the symptoms experienced right after exposure to a traumatic event, up until 48 hours after it. In contrast, ASD is defined by symptoms experienced after 48 hours of the event, up until one month past the event. Symptoms experienced for longer than one month are consistent with a diagnosis of PTSD.

Drug abuse and alcohol abuse commonly co-occur with PTSD. Recovery from posttraumatic stress disorder or other anxiety disorders may be hindered, or the condition worsened, when substance use disorders are comorbid with PTSD. Resolving these problems can bring about improvement in an individual's mental health status and anxiety levels.

An adjustment disorder (AD)—sometimes called exogenous, reactive, or situational depression—occurs when an individual is unable to adjust to or cope with a particular stress or a major life event. Since people with this disorder normally have symptoms that depressed people do, such as general loss of interest, feelings of hopelessness and crying, this disorder is sometimes known as situational depression. Unlike major depression, the disorder is caused by an outside stressor and generally resolves once the individual is able to adapt to the situation. One hypothesis about AD is that it may represent a sub-threshold clinical syndrome.

The condition is different from anxiety disorder, which lacks the presence of a stressor, or post-traumatic stress disorder and acute stress disorder, which usually are associated with a more intense stressor.

Common characteristics of AD include mild depressive symptoms, anxiety symptoms, and traumatic stress symptoms or a combination of the three. There are nine types of AD listed in the DSM-III-R. According to the DSM-IV-TR, there are six types of AD, which are characterized by the following predominant symptoms: depressed mood, anxiety, mixed depression and anxiety, disturbance of conduct, mixed disturbance of emotions and conduct, and unspecified. However, the criteria for these symptoms are not specified in greater detail. AD may be acute or chronic, depending on whether it lasts more or less than six months. According to the DSM-IV-TR, if the AD lasts less than 6 months, then it may be considered acute. If it lasts more than six months, it may be considered chronic. Moreover, the symptoms cannot last longer than six months after the stressor(s), or its consequences, have terminated. Diagnosis of AD is quite common; there is an estimated incidence of 5%–21% among psychiatric consultation services for adults. Adult women are diagnosed twice as often as are adult men. Among children and adolescents, girls and boys are equally likely to receive this diagnosis. AD was introduced into the psychiatric classification systems almost 30 years ago, but similar syndromes were recognized for many years before that.

International Statistical Classification of Diseases and Related Health Problems, mostly known as "ICD", assigns codes to classify diseases, symptoms, complaints, social behaviors, injuries, and such medical-related findings.

ICD 10 classifies adjustment disorders under F40-F48 and under neurotic, stress-related and somatoform disorders.

People who go through these types of extremely traumatic experiences often have certain symptoms and problems afterward. The severity of these symptoms depends on the person, the type of trauma involved, and the emotional support they receive from others. Reactions to and symptoms of trauma can be wide and varied, and differ in severity from person to person. A traumatized individual may experience one or several of them.

After a traumatic experience, a person may re-experience the trauma mentally and physically, hence trauma reminders, also called triggers, can be uncomfortable and even painful. It can damage people’s sense of safety, self, self-efficacy, as well as the ability to regulate emotions and navigate relationships. They may turn to psychoactive substances including alcohol to try to escape or dampen the feelings. These triggers cause flashbacks, which are dissociative experiences where the person feels as though the events is reoccurring. They can range from distracting to complete dissociation or loss of awareness of the current context. Re-experiencing symptoms are a sign that the body and mind are actively struggling to cope with the traumatic experience.

Triggers and cues act as reminders of the trauma, and can cause anxiety and other associated emotions. Often the person can be completely unaware of what these triggers are. In many cases this may lead a person suffering from traumatic disorders to engage in disruptive or self-destructive coping mechanisms, often without being fully aware of the nature or causes of their own actions. Panic attacks are an example of a psychosomatic response to such emotional triggers.

Consequently, intense feelings of anger may frequently surface, sometimes in inappropriate or unexpected situations, as danger may always seem to be present, as much as it is actually present and experienced from past events. Upsetting memories such as images, thoughts, or flashbacks may haunt the person, and nightmares may be frequent. Insomnia may occur as lurking fears and insecurity keep the person vigilant and on the lookout for danger, both day and night. Trauma doesn't only cause changes in one's daily functions but could also lead to morphological changes. Such epigenetic changes can be passed on to the next generations, thus making genetics as one of the components of the causes of psychological trauma. However, some people are born with or later develop protective factors such as genetics and sex that help lower their risk of psychological trauma.

The person may not remember what actually happened, while emotions experienced during the trauma may be re-experienced without the person understanding why (see Repressed memory). This can lead to the traumatic events being constantly experienced as if they were happening in the present, preventing the subject from gaining perspective on the experience. This can produce a pattern of prolonged periods of acute arousal punctuated by periods of physical and mental exhaustion. This can lead to mental health disorders like acute stress and anxiety disorder, traumatic grief, undifferentiated somatoform disorder, conversion disorders, brief psychotic disorder, borderline personality disorder, adjustment disorder...etc.

In time, emotional exhaustion may set in, leading to distraction, and clear thinking may be difficult or impossible. Emotional detachment, as well as dissociation or "numbing out", can frequently occur. Dissociating from the painful emotion includes numbing all emotion, and the person may seem emotionally flat, preoccupied, distant, or cold. Dissociation includes depersonalisation disorder, dissociative amnesia, dissociative fugue, dissociative identity disorder, etc. Exposure to and re-experiencing trauma can cause neurophysiological changes like slowed myelination, abnormalities in synaptic pruning, shrinking of the hippocampus, cognitive and affective impairment. This is significant in brain scan studies done regarding higher order function assessment with children and youth who were in vulnerable environments.

Some traumatized people may feel permanently damaged when trauma symptoms do not go away and they do not believe their situation will improve. This can lead to feelings of despair, transient paranoid ideation, loss of self-esteem, profound emptiness, suicidality, and frequently depression. If important aspects of the person's self and world understanding have been violated, the person may call their own identity into question. Often despite their best efforts, traumatized parents may have difficulty assisting their child with emotion regulation, attribution of meaning, and containment of post-traumatic fear in the wake of the child's traumatization, leading to adverse consequences for the child. In such instances, it is in the interest of the parent(s) and child for the parent(s) to seek consultation as well as to have their child receive appropriate mental health services.

A mental breakdown (also known as a nervous breakdown) is an acute, time-limited mental disorder that manifests primarily as severe stress-induced depression, anxiety, or dissociation in a previously functional individual, to the extent that they are no longer able to function on a day-to-day basis until the disorder is resolved. A nervous breakdown is defined by its temporary nature, and often closely tied to psychological burnout, severe overwork, sleep deprivation, and similar stressors, which may combine to temporarily overwhelm an individual with otherwise sound mental functions.

The signs are: Tachycardia (increased heart rate), Sweating, Hyperventilation (increased breathing).

The symptoms usually appear within minutes of the impact of the stressful stimulus and disappear within 2–3 days.

Symptoms show considerable variation but usually include:

An initial state of "DAZE" with some constriction of the field of consciousness and narrowing of attention, inability to comprehend stimuli, disorientation. Followed either by further withdrawal from the surrounding situation to the extent of a dissociative stupor or by agitating and over activity.

Psychological trauma is a type of damage to the mind that occurs as a result of a severely distressing event. Trauma is often the result of an overwhelming amount of stress that exceeds one's ability to cope, or integrate the emotions involved with that experience. A traumatic event involves one's experience, or repeating events of being overwhelmed that can be precipitated in weeks, years, or even decades as the person struggles to cope with the immediate circumstances, eventually leading to serious, long-term negative consequences.

However, trauma differs between individuals, according to their subjective experiences. People will react to similar events differently. In other words, not all people who experience a potentially traumatic event will actually become psychologically traumatized. However, it is possible to develop posttraumatic stress disorder (PTSD) after being exposed to a potentially traumatic event.

This discrepancy in risk rate can be attributed to protective factors some individuals may have that enable them to cope with trauma; they are related to temperamental and environmental factors. Some examples are mild exposure to stress early in life, resilience characteristics, and active seeking of help.

The terms "nervous breakdown" and "mental breakdown" have not been formally defined through a medical diagnostic system such as the DSM-5 or ICD-10, and are nearly absent from current scientific literature regarding mental illness. Although "nervous breakdown" is not rigorously defined, surveys of laypersons suggest that the term refers to a specific acute time-limited reactive disorder, involving symptoms such as anxiety or depression, usually precipitated by external stressors. Many health experts today refer to a nervous breakdown as a "modern mental health crisis."

Specific cases are sometimes described as a "breakdown" only after the emotional and physical demands on a person's life are so great as to prevent him or her from performing activities of daily living or, less strictly, only when those demands prevent him/her from performing his/her familial or occupational duties.

Nervous breakdowns are often caused by serious ongoing mental health disorders.

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.

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.

Intermittent explosive disorder (sometimes abbreviated as IED) is a behavioral disorder characterized by explosive outbursts of anger and violence, often to the point of rage, that are disproportionate to the situation at hand (e.g., impulsive screaming triggered by relatively inconsequential events). Impulsive aggression is not premeditated, and is defined by a disproportionate reaction to any provocation, real or perceived. Some individuals have reported affective changes prior to an outburst (e.g., tension, mood changes, energy changes, etc.).

The disorder is currently categorized in the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-5) under the "Disruptive, Impulse-Control, and Conduct Disorders" category. The disorder itself is not easily characterized and often exhibits comorbidity with other mood disorders, particularly bipolar disorder. Individuals diagnosed with IED report their outbursts as being brief (lasting less than an hour), with a variety of bodily symptoms (sweating, stuttering, chest tightness, twitching, palpitations) reported by a third of one sample. Aggressive acts are frequently reported accompanied by a sensation of relief and in some cases pleasure, but often followed by later remorse.

RTS identifies three stages of psychological trauma a rape survivor goes through: the acute stage, the outer adjustment stage, and the renormalization stage.

The current DSM-5 criteria for Intermittent Explosive Disorder include:

- Recurrent outbursts that demonstrate an inability to control impulses, including either of the following:

- Verbal aggression (tantrums, verbal arguments or fights) or physical aggression that occurs twice in a week-long period for at least three months and does not lead to destruction of property or physical injury (Criterion A1)

- Three outbursts that involve injury or destruction within a year-long period (Criterion A2)

- Aggressive behavior is grossly disproportionate to the magnitude of the psychosocial stressors (Criterion B)

- The outbursts are not premeditated and serve no premeditated purpose (Criterion C)

- The outbursts cause distress or impairment of functioning, or lead to financial or legal consequences (Criterion D)

- The individual must be at least six years old (Criterion E)

- The recurrent outbursts cannot be explained by another mental disorder and are not the result of another medical disorder or substance use (Criterion F)

It is important to note that DSM-5 now includes two separate criteria for types of aggressive outbursts (A1 and A2) which have empirical support:

- Criterion A1: Episodes of verbal and/or non damaging, nondestructive, or non injurious physical assault that occur, on average, twice weekly for three months. These could include temper tantrums, tirades, verbal arguments/fights, or assault without damage. This criterion includes high frequency/low intensity outbursts.

- Criterion A2: More severe destructive/assaultive episodes which are more infrequent and occur, on average, three times within a twelve-month period. These could be destroying an object without regard to value, assaulting an animal or individual. This criterion includes high-intensity/low-frequency outbursts.

The acute stage occurs in the days or weeks after a rape. Durations vary as to the amount of time the victim may remain in the acute stage. The immediate symptoms may last a few days to a few weeks and may overlap with the outward adjustment stage.

According to Scarse, there is no "typical" response amongst rape victims. However, the U.S. Rape Abuse and Incest National Network (RAINN) asserts that, in most cases, a rape victim's acute stage can be classified as one of three responses: expressed ("He or she may appear agitated or hysterical, [and] may suffer from crying spells or anxiety attacks"); controlled ("the survivor appears to be without emotion and acts as if 'nothing happened' and 'everything is fine'"); or shock/disbelief ("the survivor reacts with a strong sense of disorientation. They may have difficulty concentrating, making decisions, or doing everyday tasks. They may also have poor recall of the assault"). Not all rape survivors show their emotions outwardly. Some may appear calm and unaffected by the assault.

Behaviors present in the acute stage can include:

- Diminished alertness.

- Numbness.

- Dulled sensory, affective and memory functions.

- Disorganized thought content.

- Vomiting.

- Nausea.

- Paralyzing anxiety.

- Pronounced internal tremor.

- Obsession to wash or clean themselves.

- Hysteria, confusion and crying.

- Bewilderment.

- Acute sensitivity to the reaction of other people.

Hypomania is the signature characteristic of Bipolar II disorder. It is a state characterized by euphoria and/or an irritable mood. In order for an episode to qualify as hypomanic, the individual must also present three or more of the below symptoms, and last at least four consecutive days and be present most of the day, nearly every day

- Inflated self-esteem or grandiosity.

- Decreased need for sleep (e.g., feels rested after only 3 hours of sleep).

- More talkative than usual or pressure to keep talking.

- Flight of ideas or subjective experience that thoughts are racing.

- Distractibility (i.e., attention too easily drawn to unimportant or irrelevant external stimuli), as reported or observed.

- Increase in goal-directed activity (either socially, at work or school, or sexually) or psychomotor agitation.

- Excessive involvement in activities that have a high potential for painful consequences (e.g., engaging in unrestrained buying sprees, sexual indiscretions, or foolish business investments).

It is important to distinguish between hypomania and mania. Mania is generally greater in severity and impairs function, sometimes leading to hospitalization and in the most severe cases, psychosis. In contrast, hypomania usually increases functioning. For this reason, it is not uncommon for hypomania to go unnoticed. Often it is not until individuals are in a depressive episode that they seek treatment, and even then their history of hypomania may go undiagnosed. Even though hypomania may increase functioning, episodes need to be treated because they may precipitate a depressive episode.

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.

Dissociative disorder not otherwise specified (DDNOS) is a mental health diagnosis for pathological dissociation that matches the DSM-5 criteria for a dissociative disorder, but does not fit the full criteria for any of the specifically identified subtypes, which include dissociative identity disorder, dissociative amnesia, and depersonalization/derealization disorder. The International Statistical Classification of Diseases and Related Health Problems (ICD-10) refers to the diagnosis as "Other dissociative and conversion disorders".

Examples of DDNOS include chronic and recurrent syndromes of mixed dissociative symptoms, identity disturbance due to prolonged and intense coercive persuasion, disorders similar to dissociative identity disorder, acute dissociative reactions to stressful events, and dissociative trance.

DDNOS is the most common dissociative disorder and is diagnosed in 40% of dissociative disorder cases. It is often co-morbid with other mental illnesses such as complex posttraumatic stress disorder, major depressive disorder, generalized anxiety disorder, personality disorders, substance abuse disorders and eating disorders.

Generalized anxiety disorder (GAD) is a common disorder, characterized by long-lasting anxiety that is not focused on any one object or situation. Those suffering from generalized anxiety disorder experience non-specific persistent fear and worry, and become overly concerned with everyday matters. Generalized anxiety disorder is "characterized by chronic excessive worry accompanied by three or more of the following symptoms: restlessness, fatigue, concentration problems, irritability, muscle tension, and sleep disturbance". Generalized anxiety disorder is the most common anxiety disorder to affect older adults. Anxiety can be a symptom of a medical or substance abuse problem, and medical professionals must be aware of this. A diagnosis of GAD is made when a person has been excessively worried about an everyday problem for six months or more. A person may find that they have problems making daily decisions and remembering commitments as a result of lack of concentration/preoccupation with worry. Appearance looks strained, with increased sweating from the hands, feet, and axillae, and they may be tearful, which can suggest depression. Before a diagnosis of anxiety disorder is made, physicians must rule out drug-induced anxiety and other medical causes.

In children GAD may be associated with headaches, restlessness, abdominal pain, and heart palpitations. Typically it begins around 8 to 9 years of age.

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.

The most common stress reactions include:

- The slowing of reaction time

- Slowness of thought

- Difficulty prioritizing tasks

- Difficulty initiating routine tasks

- Preoccupation with minor issues and familiar tasks

- Indecision and lack of concentration

- Loss of initiative with fatigue

- Exhaustion

Combat stress reaction symptoms align with the symptoms also found in psychological trauma, which is closely related to post-traumatic stress disorder (PTSD). CSR differs from PTSD (among other things) in that a PTSD diagnosis requires a duration of symptoms over one month, which CSR does not.