Medical conditions associated with an increased risk of PTSD include cancer, heart attack, and stroke. Intensive-care unit (ICU) hospitalization is also a risk factor for PTSD. Some women experience PTSD from their experiences related to breast cancer and mastectomy.

MIltiary service is a risk factor for developing PTSD. Around 78% of people exposed to combat do not develop PTSD; in about 25% of military personnel who develop PTSD, its appearance is delayed.

Refugees are also at an increased risk for PTSD due to their exposure to war, hardships, and traumatic events. The rates for PTSD within refugee populations range from 4% to 86%. While the stresses of war impact everyone involved, displaced persons have been shown to be more affected than nondisplaced persons.

Various factors have been found to be more associated with a diagnosis of AD than other axis I disorders, including:

- younger age

- more identified psychosocial and environmental problems

- increased suicidal behaviour, more likely to be rated as improved by the time of discharge from mental healthcare

- less frequent previous psychiatric history

- shorter length of treatment

Those exposed to repeated trauma are at greater risk, even if that trauma is in the distant past. Age can be a factor due to young children having fewer coping resources; children are also less likely to assess the consequences of a potential stressor.

A stressor is generally an event of a serious, unusual nature that an individual or group of individuals experience. The stressors that cause adjustment disorders may be grossly traumatic or relatively minor, like loss of a girlfriend/boyfriend, a poor report card, or moving to a new neighborhood. It is thought that the more chronic or recurrent the stressor, the more likely it is to produce a disorder. The objective nature of the stressor is of secondary importance. Stressors' most crucial link to their pathogenic potential is their perception by the patient as stressful. The presence of a causal stressor is essential before a diagnosis of adjustment disorder can be made.

There are certain stressors that are more common in different age groups:

Adulthood:

- Marital conflict

- Financial conflict

- Health issues with Oneself/Partner or Dependent children

- Personal tragedy (Death/personal loss)

- Loss of job or unstable employment conditions (e.g. Corporate takeover/redundancy)

Adolescence and childhood:

- Family conflict/parental separation

- School problems/changing schools

- Sexuality issues

- Death/illness/trauma in the family

In a study conducted from 1990 to 1994 on 89 psychiatric outpatient adolescents, 25% had attempted suicide in which 37.5% had misused alcohol, 87.5% displayed aggressive behaviour, 12.5% had learning difficulties, and 87.5% had anxiety symptoms.

The causes of PTSD are: Natural or human disasters, war, serious accident, witness of violent death of others, violent attack, being the victim of sexual abuse, rape, torture, terrorism or hostage taking.

Predisposing factors

The predisposing factors are: Personality traits and Previous history of Psychiatric illness.

According to the DSM IV-TR, the development of the emotional or behavioral symptoms of this diagnosis have to occur within three months of the onset of the identifiable stressor(s). Some emotional signs of adjustment disorder are:

However, the stress-related disturbance does not only exist as an exacerbation of a pre-existing axis I or axis II disorder and cannot be diagnostic as axis 1 disorder.

Suicidal behavior is prominent among people with AD of all ages, and up to one-fifth of adolescent suicide victims may have an adjustment disorder. Bronish and Hecht (1989) found that 70% of a series of patients with AD attempted suicide immediately before their index admission and they remitted faster than a comparison group with major depression. Asnis et al. (1993) found that AD patients report persistent ideation or suicide attempts less frequently than those diagnosed with major depression. According to a study on 82 AD patients at a clinic, Bolu et al. (2012) found that 22 (26.8%) of these patients were admitted due to suicide attempt, consistent with previous findings. In addition, it was found that 15 of these 22 patients chose suicide methods that involved high chances of being saved. Henriksson et al. (2005) states statistically that the stressors are of one-half related to parental issues and one-third in peer issues.

Vicarious trauma affects workers being 'witnesses' to their clients' trauma. It is more likely to occur in situations where trauma related work is the norm rather than the exception. Listening with empathy to the clients generates feeling, and 'seeing oneself' in clients' trauma may compound the risk for developing trauma symptoms. May also result if we are witness to situations that happen in the course of our work (e.g. violence in the workplace, reviewing violent video tapes, etc.). Risk increases with exposure and with the absence of seeking protective factors and pre-preparation of preventive strategies.

There are several theoretical perspectives on trauma response, including cognitive, biological, and psychobiological. While the theories are PTSD-specific, they are still useful in understanding ASD, as both share many symptoms.

Acute stress disorder (abbreviated ASD, and not to be confused with autism spectrum disorder) is the result of a traumatic event in which the person experiences or witnesses an event that causes the victim/witness to experience extreme, disturbing, or unexpected fear, stress, or pain, and that involves or threatens serious injury, perceived serious injury, or death to themselves or someone else. A study of rescue personnel after exposure to a traumatic event showed no gender difference in acute stress reaction. Acute stress reaction is a variation of post-traumatic stress disorder (PTSD).

A recent study found that a "single" stressful event may cause long-term consequences in the brain. This result calls the traditional distinction between the effects of acute vs chronic stress into question.

Psychiatric consultation: Exploration of memories of the traumatic event, relief of associated symptoms and counseling.

Acute stress reaction (also called acute stress disorder, psychological shock, mental shock, or simply shock) is a psychological condition arising in response to a terrifying or traumatic event, or witnessing a traumatic event that induces a strong emotional response within the individual. It should not be confused with the unrelated circulatory condition of shock/hypoperfusion. Acute stress reaction (ASR) may develop into delayed stress reaction (better known as PTSD) if stress is not correctly managed. ASR is characterized by re-living and avoiding reminders of an aversive event, as well as generalized hypervigilance after initial exposure to a traumatic event. ASD is differentiated from PTSD as a disorder that precedes it, and if symptoms last for more than one month, it will develop into PTSD. It can thus be thought of as the acute phase of PTSD.

All psychological traumas originate from stress, a physiological response to an unpleasant stimulus. Long term stress increases the risk of poor mental health and mental disorders, which can be attributed to secretion of glucocorticoids for a long period of time. Such prolonged exposure causes many physiological dysfunctions such as the suppression of the immune system and increase in blood pressure. Not only does it affect the body physiologically, but a morphological change in the hippocampus also takes place. Studies showed that extreme stress early in life can disrupt normal development of hippocampus and impact its functions in adulthood. Studies surely show a correlation between the size of hippocampus and one's susceptibility to stress disorders. In times of war, psychological trauma has been known as shell shock or combat stress reaction. Psychological trauma may cause an acute stress reaction which may lead to posttraumatic stress disorder (PTSD). PTSD emerged as the label for this condition after the Vietnam War in which many veterans returned to their respective countries demoralized, and sometimes, addicted to psychoactive substances. The symptoms of PTSD must persist for at least a month for diagnosis. The main symptoms of PTSD consist of four main categories: Trauma (i.e. intense fear), reliving (i.e. flashbacks), avoidance behavior (i.e. emotional numbing), and hypervigilance (i.e. irritability). Research shows that about 60% of the US population reported as having experienced at least one traumatic symptom in their lives but only a small proportion actually develops PTSD. There is a correlation between the risk of PTSD and whether or not the act was inflicted deliberately by the offender. Psychological trauma is treated with therapy and, if indicated, psychotropic medications.

The term "continuous post traumatic stress disorder" (CTSD) was introduced into the trauma literature by Gill Straker (1987). It was originally used by South African clinicians to describe the effects of exposure to frequent, high levels of violence usually associated with civil conflict and political repression. The term is also applicable to the effects of exposure to contexts in which gang violence and crime are endemic as well as to the effects of ongoing exposure to life threats in high-risk occupations such as police, fire and emergency services.

As one of the processes of treatment, confrontation with their sources of trauma plays a crucial role. While critical incident debriefing people immediately after an event has not been shown to reduce incidence of PTSD, coming alongside people experiencing trauma in a supportive way has become standard practice.

Several studies have shown that the risk of suicide is higher in patients who suffer from Bipolar II than those who suffer from Bipolar I, and especially higher than patients who suffer from major depressive disorder.

In results of a summary of several lifetime study experiments, it was found that 24% of Bipolar II patients experienced suicidal ideation or suicide attempts compared to 17% in Bipolar I patients and 12% in major depressive patients. Bipolar disorders, in general, are the third leading cause of death in 15- to 24-year-olds. Bipolar II patients were also found to employ more lethal means and have more complete suicides overall.

Bipolar II patients have several risk factors that increase their risk of suicide. The illness is very recurrent and results in severe disabilities, interpersonal relationship problems, barriers to academic, financial, and vocational goals, and a loss of social standing in their community, all of which increase the likelihood of suicide. Mixed symptoms and rapid-cycling, both very common in Bipolar II, are also associated with an increased risk of suicide. The tendency for Bipolar II to be misdiagnosed and treated ineffectively, or not at all in some cases, leads to an increased risk.

As a result of the high suicide risk for this group, reducing the risk and preventing attempts remains a main part of the treatment; a combination of self-monitoring, close supervision by a therapist, and faithful adherence to their medication regimen will help to reduce the risk and prevent the likelihood of a completed suicide.

There are no known biological causes that apply consistently to all cases of dysthymia, which suggests diverse origin of the disorder. However, there are some indications that there is a genetic predisposition to dysthymia: "The rate of depression in the families of people with dysthymia is as high as fifty percent for the early-onset form of the disorder". Other factors linked with dysthymia include stress, social isolation, and lack of social support.

In a study using identical and fraternal twins, results indicated that there is a stronger likelihood of identical twins both having depression than fraternal twins. This provides support for the idea that dysthymia is in part caused by heredity.

Comorbid conditions are extremely common in individuals with BP-II. In fact, individuals are twice as likely to present a comorbid disorder than not. These include anxiety, eating, personality (cluster B), and substance use disorders. For bipolar II disorder, the most conservative estimate of lifetime prevalence of alcohol or other drug abuse disorders is 20%. In patients with comorbid substance abuse disorder and BP-II, episodes have a longer duration and treatment compliance decreases. Preliminary studies suggest that comorbid substance abuse is also linked to increased risk of suicidality.

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.

Impulsive behavior, and especially impulsive violence predisposition has been correlated to a low brain serotonin turnover rate, indicated by a low concentration of 5-hydroxyindoleacetic acid (5-HIAA) in the cerebrospinal fluid (CSF). This substrate appears to act on the suprachiasmatic nucleus in the hypothalamus, which is the target for serotonergic output from the dorsal and median raphe nuclei playing a role in maintaining the circadian rhythm and regulation of blood sugar. A tendency towards low 5-HIAA may be hereditary. A putative hereditary component to low CSF 5-HIAA and concordantly possibly to impulsive violence has been proposed. Other traits that correlate with IED are low vagal tone and increased insulin secretion. A suggested explanation for IED is a polymorphism of the gene for tryptophan hydroxylase, which produces a serotonin precursor; this genotype is found more commonly in individuals with impulsive behavior.

IED may also be associated with lesions in the prefrontal cortex, with damage to these areas, including the amygdala, increasing the incidence of impulsive and aggressive behavior and the inability to predict the outcomes of an individual's own actions. Lesions in these areas are also associated with improper blood sugar control, leading to decreased brain function in these areas, which are associated with planning and decision making. A national sample in the United States estimated that 16 million Americans may fit the criteria for IED.

"At least three-quarters of patients with dysthymia also have a chronic physical illness or another psychiatric disorder such as one of the anxiety disorders, cyclothymia, drug addiction, or alcoholism". Common co-occurring conditions include major depression (up to 75%), anxiety disorders (up to 50%), personality disorders (up to 40%), somatoform disorders (up to 45%) and substance abuse (up to 50%). People with dysthymia have a higher-than-average chance of developing major depression. A 10-year follow-up study found that 95% of dysthymia patients had an episode of major depression. When an intense episode of depression occurs on top of dysthymia, the state is called "double depression."

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.

Two epidemiological studies of community samples approximated the lifetime prevalence of IED to be 4–6%, depending on the criteria set used. A Ukrainian study found comparable rates of lifetime IED (4.2%), suggesting that a lifetime prevalence of IED of 4–6% is not limited to American samples. One-month and one-year point prevalences of IED in these studies were reported as 2.0% and 2.7%, respectively. Extrapolating to the national level, 16.2 million Americans would have IED during their lifetimes and as many as 10.5 million in any year and 6 million in any month.

Among a "clinical" population, a 2005 study found the lifetime prevalence of IED to be 6.3%.

Prevalence appears to be higher in men than in women.

Of US subjects with IED, 67.8% had engaged in direct interpersonal aggression, 20.9% in threatened interpersonal aggression, and 11.4% in aggression against objects. Subjects reported engaging in 27.8 high-severity aggressive acts during their worst year, with 2–3 outbursts requiring medical attention. Across the lifespan, the mean value of property damage due to aggressive outbursts was $1603.

A study in the March 2016 "Journal of Clinical Psychiatry" suggests a relationship between infection with the parasite "Toxoplasma gondii" and psychiatric aggression such as IED.

Bipolar disorder can cause suicidal ideation that leads to suicidal attempts. Individuals whose bipolar disorder begins with a depressive or mixed affective episode seem to have a poorer prognosis and an increased risk of suicide. One out of two people with bipolar disorder attempt suicide at least once during their lifetime and many attempts are successfully completed. The annual average suicide rate is 0.4 percent, which is 10–20 times that of the general population. The standardized mortality ratio from suicide in bipolar disorder is between 18 and 25. The lifetime risk of suicide has been estimated to be as high as 20 percent in those with bipolar disorder.

GAD runs in families and is six times more common in the children of someone with the condition.

While anxiety arose as an adaptation, in modern times it is almost always thought of negatively in the context of anxiety disorders. People with these disorders have highly sensitive systems; hence, their systems tend to overreact to seemingly harmless stimuli. Sometimes anxiety disorders occur in those who have had traumatic youths, demonstrating an increased prevalence of anxiety when it appears a child will have a difficult future. In these cases, the disorder arises as a way to predict that the individual’s environment will continue to pose threats.

At a low level, anxiety is not a bad thing. In fact, the hormonal response to anxiety has evolved as a benefit, as it helps humans react to dangers. Researchers in evolutionary medicine believe this adaptation allows humans to realize there is a potential threat and to act accordingly in order to ensure greatest possibility of protection. It has actually been shown that those with low levels of anxiety have a greater risk of death than those with average levels. This is because the absence of fear can lead to injury or death. Additionally, patients with both anxiety and depression were found to have lower morbidity than those with depression alone. The functional significance of the symptoms associated with anxiety includes: greater alertness, quicker preparation for action, and reduced probability of missing threats. In the wild, vulnerable individuals, for example those who are hurt or pregnant, have a lower threshold for anxiety response, making them more alert. This demonstrates a lengthy evolutionary history of the anxiety response.

Depressed mood can be the result of a number of infectious diseases, nutritional deficiencies, neurological conditions and physiological problems, including hypoandrogenism (in men), Addison's disease, Cushing's syndrome, hypothyroidism, Lyme disease, multiple sclerosis, Parkinson's disease, chronic pain, stroke, diabetes, and cancer.

Schizoaffective disorder is estimated to occur in 0.5 to 0.8 percent of people at some point in their life. It is more common in women than men; however, this is because of the high concentration of women in the depressive subcategory, whereas the bipolar subtype has a more or less even gender distribution.

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

Studies have shown that those who fall into minorities due to either their gender identity or sexual orientation (such as those that identify as LGBT), are more prone to depression.