When patterns of thought, emotion, or behavior cause significant distress or impairment, psychologists may diagnose a psychological disorder. The standard reference used by mental health professionals in the United States is the Diagnostic and Statistical Manual of Mental Disorders, now in its fifth edition, known as the DSM-5, which provides criteria for identifying specific conditions and distinguishing them from ordinary variations in human experience.
Anxiety disorders are among the most common forms of psychopathology. Generalized anxiety disorder, or GAD, is characterized by persistent, excessive worry about many everyday matters for at least six months, accompanied by symptoms such as restlessness, fatigue, difficulty concentrating, and sleep disturbance. Phobias are related but more specific, consisting of intense, irrational fears of particular objects or situations, such as spiders or heights, rather than the diffuse worry of GAD. Obsessive-compulsive disorder, or OCD, is marked by unwanted, intrusive thoughts called obsessions and by repetitive behaviors called compulsions that are performed to reduce anxiety; common examples include excessive handwashing or repeatedly checking locks. Post-traumatic stress disorder, or PTSD, develops after exposure to a traumatic event and features flashbacks, nightmares, hypervigilance, avoidance of reminders, and emotional numbing lasting more than one month.
Mood disorders are another major category. Major depressive disorder, or MDD, involves persistent feelings of sadness, hopelessness, and loss of interest in activities for at least two weeks, often accompanied by changes in sleep, appetite, energy, and concentration, and in some cases suicidal thoughts. Bipolar disorder is characterized by alternating episodes of mania, marked by elevated mood, high energy, and impulsivity, and depression; Bipolar I includes full manic episodes, while Bipolar II includes less severe hypomanic episodes along with depressive ones. Schizophrenia is a particularly severe disorder characterized by distorted thinking, hallucinations, delusions, and disorganized speech or behavior, typically emerging in late adolescence or early adulthood. Its symptoms are divided into positive symptoms, which are excesses such as hallucinations and delusions, and negative symptoms, which are deficits such as flat affect, social withdrawal, reduced motivation, and poverty of speech. Finally, antisocial personality disorder is characterized by a persistent pattern of disregard for the rights of others, including deceit, impulsivity, aggression, and a notable lack of remorse, and is often associated with criminal behavior.