Types of Psychological Disorders

The DSM organizes psychological disorders into named categories, each defined by its own characteristic pattern of symptoms. This article surveys the major categories tested on the MCAT — psychotic, depressive, bipolar, anxiety, obsessive-compulsive, trauma- and stressor-related, dissociative, somatic symptom, and personality disorders — along with the specific features that distinguish each disorder from others that can look similar on the surface.

Key Takeaways

• Schizophrenia requires ≥6 months of continuous disturbance with ≥1 month of active symptoms, and its symptoms split into positive (delusions, hallucinations, disorganized thought/behavior, catatonia) and negative (flat affect, avolition) categories.

• Depressive disorders include major depressive disorder (≥5 of 9 symptoms over a 2-week period, including depressed mood or anhedonia), persistent depressive disorder (dysthymia ≥2 years), and seasonal affective disorder (a seasonal-onset presentation, not a standalone DSM diagnosis).

• Bipolar I requires a manic episode; bipolar II requires hypomania plus a major depressive episode — the monoamine/catecholamine theory links excess norepinephrine/serotonin to mania and deficits to depression.

• Anxiety disorders are distinguished by their trigger: generalized worry (GAD), a specific object/situation (specific phobia), social/performance situations (social anxiety disorder), inability to escape (agoraphobia), or recurrent unexpected attacks (panic disorder).

• OCD (ego-dystonic, obsessions and tension-relieving compulsions) is distinct from body dysmorphic disorder (appearance-focused) and from OCPD (ego-syntonic, lifelong personality trait).

• PTSD (intrusion, avoidance, negative cognitive, and arousal symptoms, >1 month) is distinguished from acute stress disorder (same symptoms, 3 days–1 month) primarily by duration.

• Dissociative disorders — amnesia, fugue, and dissociative identity disorder — center on escaping stress through disruptions in memory or identity, without psychotic symptoms.

• Somatic symptom and related disorders — somatic symptom disorder, illness anxiety disorder, and conversion disorder — involve physical symptoms or health preoccupation without a proportionate underlying medical cause.

• Personality disorders are ego-syntonic, inflexible, and maladaptive, organized into Cluster A (odd/eccentric: paranoid, schizotypal, schizoid), Cluster B (dramatic/emotional/erratic: antisocial, borderline, histrionic, narcissistic), and Cluster C (anxious/fearful: avoidant, dependent, OCPD).

Schizophrenia

Schizophrenia is the prototypical psychotic disorder. A psychotic disorder involves one or more of the following: delusions, hallucinations, disorganized thought, disorganized behavior, catatonia, and other negative symptoms.

To be diagnosed with schizophrenia, a person must show continuous signs of disturbance for at least six months, with at least one month including active symptoms — delusions, hallucinations, or disorganized speech.

Schizophrenia's symptoms fall into two categories:

• Positive symptoms are behaviors, thoughts, or feelings added to normal experience — delusions, hallucinations, disorganized thought, and disorganized or catatonic behavior. These are sometimes split into two distinct dimensions: a psychotic dimension and a disorganized dimension.

• Negative symptoms involve the absence of normal or expected behavior — disturbance of affect and avolition (decreased motivation).

Positive Symptoms

Delusions are false beliefs that don't align with reality and aren't shared by others in the individual's culture. They're maintained despite strong evidence to the contrary. Several specific subtypes appear on the MCAT:

• Delusion of reference: the belief that common elements in the environment are directed at the individual (e.g., believing that characters on a TV show are speaking directly to them).

• Delusion of persecution: the belief that one is being deliberately interfered with, discriminated against, plotted against, or threatened.

• Delusion of grandeur: the belief that one is remarkable in some significant way; common in bipolar disorder.

• Thought broadcasting: the belief that one's thoughts are being broadcast directly from one's head to the external world.

• Thought insertion: the belief that thoughts are being placed into one's head by an outside source.

Hallucinations are perceptions not caused by external stimuli but that seem like reality. Auditory hallucinations (hearing voices) are the most common form. Visual and tactile hallucinations are less common but can occur with drug use or withdrawal. Olfactory and gustatory hallucinations are rarer still, but can occur just before a seizure.

Disorganized thought is characterized by a loosening of associations — a listener is unable to follow the speaker's train of thought, and speech can seem so disorganized it appears to have no structure at all (sometimes called "word salad"). Neologisms — invented words — are another feature of disorganized thought in schizophrenia.

Disorganized behavior is an inability to carry out activities of daily living, such as paying bills, maintaining hygiene, and keeping appointments.

Catatonia refers to a set of abnormal motor behaviors seen in some people with schizophrenia. Spontaneous movement and activity may be reduced, or the person may maintain a rigid posture and refuse to move. At the opposite extreme, catatonia can involve useless, bizarre movements not triggered by any external stimulus, echolalia (repeating another person's words), or echopraxia (imitating another person's actions).

Negative Symptoms

Disturbance of affect refers to changes in the experience and outward display of emotion:

• Blunting: a severe reduction in the intensity of expressed affect.

• Flat affect (emotional flattening): no outward signs of emotional expression at all.

• Inappropriate affect: affect that's clearly discordant with the content of the person's speech.

Avolition is decreased engagement in purposeful, goal-directed action.

MCAT Callout — Positive vs. negative symptoms: the fastest way to sort a symptom is to ask whether it's something added to normal behavior or something missing from it. Delusions, hallucinations, disorganized thought/behavior, and catatonia are all things added — positive symptoms. Flat affect and avolition are things missing — negative symptoms. A vignette describing a patient hearing voices is describing a positive symptom; one describing a patient who has stopped showing any emotion is describing a negative symptom.

Prodromal Phase

The prodromal phase precedes the onset of schizophrenia and is characterized by poor adjustment — clear evidence of deterioration, social withdrawal, impaired role functioning, peculiar behavior, inappropriate affect, and unusual experiences. It's followed by the active phase of symptoms. Schizophrenia's prognosis is best when the onset of symptoms is intense and sudden, rather than gradual.

Depressive Disorders

Major Depressive Disorder

Major depressive disorder is a mood disorder defined by at least one major depressive episode. A major depressive episode requires five or more of the following symptoms present during the same two-week period, representing a change from the person's previous functioning, with at least one of the symptoms being depressed mood or anhedonia:

• Anhedonia: loss of interest in all or almost all formerly enjoyable activities.

• Depressed mood.

• Appetite disturbances or substantial weight changes.

• Sleep disturbances.

• Decreased energy.

• Feelings of worthlessness or excessive guilt.

• Difficulty concentrating or thinking.

• Psychomotor symptoms (e.g., feeling noticeably slowed down).

• Thoughts of death or attempts at suicide.

These symptoms must cause significant distress or impairment in the person's functioning to meet criteria for a major depressive episode.

Persistent depressive disorder describes individuals who suffer from dysthymia — a depressed mood that isn't severe enough to meet the criteria for a major depressive episode — for at least two years. The diagnosis can also be given to individuals whose major depressive disorder lasts at least two years. A person with persistent depressive disorder may experience a combination of major depressive episodes and dysthymia over that period.

Seasonal Affective Disorder (SAD)

Seasonal affective disorder is a major depressive presentation characterized by seasonal onset; it isn't a freestanding diagnosis in the DSM-5. Depressive symptoms appear only during winter months and may be related to abnormal melatonin metabolism. It's often treated with bright light therapy, in which the patient is exposed to a bright light for a specific amount of time each day.

Bipolar and Related Disorders

Bipolar and related disorders are a major type of mood disorder characterized by both depression and mania.

A manic episode is an abnormal and persistently elevated mood lasting at least one week, with at least three of the following present:

• Increased distractibility.

• Decreased need for sleep.

• Inflated self-esteem or grandiosity.

• Racing thoughts.

• Increased goal-directed activity or agitation.

• Pressured speech or increased talkativeness.

• Involvement in high-risk behavior.

Manic episodes have a rapid onset and a briefer duration than depressive episodes, and may include psychosis.

• Bipolar I disorder: manic episodes, with or without major depressive episodes.

• Bipolar II disorder: hypomania with at least one major depressive episode.

Hypomania does not significantly impair functioning and doesn't have psychotic features — the individual may simply seem more energetic and optimistic. Cyclothymic disorder is a combination of hypomanic episodes and periods of dysthymia that aren't severe enough to qualify as a major depressive episode.

MCAT Callout — Bipolar I vs. bipolar II: the distinction isn't "more severe" vs. "less severe" bipolar disorder — it's about which specific episode type is present. Bipolar I requires a full manic episode (depressive episodes are optional). Bipolar II requires hypomania plus at least one major depressive episode — a person with bipolar II never has a full manic episode by definition. If a vignette describes psychosis during an elevated mood episode, that's mania, which rules out bipolar II.

Monoamine or Catecholamine Theory of Depression

The monoamine (or catecholamine) theory of depression proposes a biochemical explanation for mood disorders: too much norepinephrine and serotonin in the synapse may lead to mania, while too little of these neurotransmitters may lead to depression.

Anxiety Disorders

Anxiety disorders are the most common category of psychiatric disorder in women of all ages; substance use disorder is the most common psychiatric disorder in men.

Generalized anxiety disorder (GAD) is common in the general population and is defined by disproportionate, persistent worry about many different things. Individuals often report physical symptoms like fatigue, muscle tension, and sleep disturbance.

A phobia is an irrational fear of something that produces a compelling desire to avoid it. Phobias are the most common type of anxiety disorder. A specific phobia is anxiety produced by a specific object or situation.

Social anxiety disorder is anxiety due to social situations — individuals have a persistent fear of exposure to social or performance situations that might result in embarrassment.

Agoraphobia is anxiety caused by fear of being in places or situations where it might be hard to escape; individuals with agoraphobia tend to be uncomfortable leaving their homes for fear of having a panic attack.

Panic disorder consists of repeated panic attacks. Symptoms of a panic attack include fear and apprehension, trembling, sweating, hyperventilation, and a sense of unreality. People experiencing a panic attack are suddenly struck by a sense of impending doom and may become convinced they're about to lose their mind. Panic disorder tends to be treated over a long period of time because it's prone to recurrence, and it's frequently accompanied by agoraphobia.

Obsessive-Compulsive and Related Disorders

Obsessive-compulsive disorder (OCD) is characterized by obsessions, which produce tension, and compulsions — repetitive tasks that relieve that tension but cause significant impairment in the person's life. The obsession raises the person's stress level, and the compulsion relieves it; the relationship between the two is central to the disorder, and the two tend to balance each other.

Body dysmorphic disorder involves an unrealistic, negative evaluation of one's own appearance and attractiveness. This body-image preoccupation disrupts day-to-day life, and the person may seek multiple cosmetic surgeries or other extreme interventions to address it.

Trauma- and Stressor-Related Disorders

Posttraumatic stress disorder (PTSD) occurs after experiencing or witnessing a traumatic event and consists of four symptom clusters:

• Intrusion symptoms: recurrent reliving of the event, flashbacks, nightmares, and prolonged distress.

• Avoidance symptoms: deliberate attempts to avoid memories, people, places, activities, and objects associated with the trauma.

• Negative cognitive symptoms: inability to recall key features of the event, negative mood or emotions, feeling distanced from others, and a persistent negative view of the world.

• Arousal symptoms: increased startle response, irritability, anxiety, self-destructive or reckless behavior, and sleep disturbances.

PTSD is diagnosed when a sufficient number of these symptoms persist for at least one month. Acute stress disorder involves the same symptom profile but lasts less than one month and more than three days.

Dissociative Disorders

Dissociative disorders reflect a person avoiding stress by escaping from their own identity.

Dissociative amnesia is characterized by an inability to recall past experiences. "Dissociative" here simply means the amnesia isn't due to a neurological disorder — it's often linked to trauma instead. Dissociative fugue is a sudden, unexpected move or purposeless wandering away from one's home, which can occur in some individuals with this type of amnesia; people in a fugue state are confused about their identity and can sometimes assume a new one.

Dissociative identity disorder (DID) involves two or more personalities that recurrently take control of a person's behavior. It results when the components of identity fail to integrate, and it's most often associated with children who have been subject to sexual or physical abuse. With extensive therapy, the separate personalities can sometimes be integrated into one.

Depersonalization/derealization disorder involves two related but distinct experiences, which can occur separately or together:

• Depersonalization: feeling detached from one's own mind and body.

• Derealization: feeling detached from one's surroundings.

A person with this disorder may have a feeling of automation and may fail to recognize their own reflection. Depersonalization is sometimes described as an out-of-body experience, while derealization is described as a dream-like world. Both cause significant impairment of regular activities, but — unlike a psychotic disorder — the individual doesn't display delusions or hallucinations.

Somatic Symptom and Related Disorders

Somatic symptom disorder involves at least one somatic (bodily) symptom that may or may not be linked to an underlying medical condition. The symptom is accompanied by disproportionate concern about its seriousness, an excessive amount of time and energy devoted to it, or elevated anxiety.

Illness anxiety disorder is characterized by preoccupation with the thought of having or developing a serious medical condition. Individuals with this disorder are quick to become alarmed about their health, and either excessively check themselves for signs of illness or avoid medical appointments altogether.

Conversion disorder is characterized by unexplained symptoms affecting voluntary motor or sensory function — for example, paralysis or blindness with no attributable neurological damage. Symptoms typically begin after the person experiences high levels of stress or a traumatic event. A distinctive feature is la belle indifférence, in which the person seems unconcerned by their own symptom. Sometimes the symptom connects to the triggering event in a literal or poetic way — for example, a woman going blind shortly after watching her son die tragically.

Personality Disorders

A personality disorder is a pattern of behavior that's inflexible and maladaptive, causing distress or impaired functioning in at least two of the following: cognition, emotions, interpersonal functioning, and impulse control.

Personality disorders are considered ego-syntonic — the individual perceives their own behavior as correct, normal, or in harmony with their goals. Most other psychological disorders are ego-dystonic — the individual experiences the illness as something thrust upon them, intrusive and bothersome.

Personality disorders are organized into three clusters:

Cluster A: Paranoid, Schizotypal, and Schizoid Personality Disorders

This cluster is marked by behaviors others tend to label as odd or eccentric.

• Paranoid personality disorder: a pervasive distrust of others. Affected individuals may be in the prodromal phase of schizophrenia, and are termed premorbid in that context.

• Schizotypal personality disorder: a pattern of odd or eccentric thinking. Individuals have ideas of reference (a less extreme version of a delusion of reference) and magical thinking, such as superstitiousness or a belief in clairvoyance.

• Schizoid personality disorder: a pervasive pattern of detachment from social relationships and a restricted range of emotional expression. Individuals show little desire for social interaction, have few if any close friends, and have poor social skills.

Cluster B: Antisocial, Borderline, Histrionic, and Narcissistic Personality Disorders

This cluster is marked by behaviors others tend to label as dramatic, emotional, or erratic.

• Antisocial personality disorder: a pattern of disregard for and violation of the rights of others. It's roughly three times more common in males than in females, and is evidenced by repeated illegal acts, deceitfulness, aggressiveness, and a lack of remorse — many serial killers and incarcerated individuals meet criteria for this disorder.

• Borderline personality disorder: pervasive instability in interpersonal behavior, mood, and self-image. It's diagnosed at roughly a 3:1 female-to-male ratio in clinical settings — though this diagnostic gap is now thought to largely reflect differences in who seeks treatment rather than a true difference in how common the disorder actually is between men and women. Affected individuals have intense, unstable interpersonal relationships; a profound identity disturbance (uncertainty about self-image, sexual identity, long-term goals, or values); and an intense fear of abandonment. They may use splitting as a defense mechanism, viewing others as all good or all evil, and suicide attempts or self-mutilation are common.

• Histrionic personality disorder: constant attention-seeking behavior. Individuals wear colorful clothing, are dramatic, and are exceptionally extroverted, and may use seductive behavior to gain attention.

• Narcissistic personality disorder: a grandiose sense of self-importance and uniqueness, preoccupation with fantasies of success, a need for constant admiration and attention, and characteristic disturbances in interpersonal relationships, including feelings of entitlement. These individuals have very fragile self-esteem and are constantly concerned with how others view them, marked by feelings of rage, inferiority, shame, humiliation, or emptiness when they aren't viewed favorably by others.

Cluster C: Avoidant, Dependent, and Obsessive-Compulsive Personality Disorders

This cluster is marked by behaviors others tend to label as anxious or fearful.

• Avoidant personality disorder: extreme shyness and fear of rejection. Affected individuals see themselves as socially inept and are often socially isolated, despite having an intense desire for social affection and acceptance. They tend to stay in the same jobs, life situations, and relationships even when they want change.

• Dependent personality disorder: a continuous need for reassurance. Individuals tend to remain dependent on one specific person to take actions and make decisions for them.

• Obsessive-compulsive personality disorder (OCPD): a perfectionistic, inflexible personality that tends to favor rules and order — for example, an inability to discard worn-out objects, a lack of desire to change, excessive stubbornness, a lack of a sense of humor, and rigid adherence to careful routines.

MCAT Callout — OCD vs. OCPD: these sound alike but aren't the same disorder. OCD is ego-dystonic — the person is distressed by their own obsessions and compulsions and typically recognizes they're excessive. It's also focal and often acquired later in life. OCPD is ego-syntonic — the perfectionism and rigidity feel correct and normal to the person, and it's a lifelong personality pattern rather than a specific, acquired set of obsessions and compulsions.

Why Types of Psychological Disorders Matters for the MCAT

MCAT questions on this material typically present a vignette describing a patient's symptoms and ask the reader to identify the disorder, or to distinguish it from a similar-looking one:

• Sort symptoms into positive vs. negative before naming the disorder. For schizophrenia specifically, first classify whether a described symptom is something added (positive) or missing (negative), since many questions hinge on this classification alone.

• Mania vs. hypomania is the hinge between bipolar I and bipolar II. A vignette describing psychosis or severe impairment during an elevated mood episode points to mania (bipolar I); one describing a milder elevated episode without impairment points to hypomania (bipolar II, if a major depressive episode is also present).

• Match the anxiety disorder to its trigger. A specific object or situation points to a specific phobia; social/performance situations point to social anxiety disorder; fear of being unable to escape points to agoraphobia; recurrent, unexpected attacks point to panic disorder.

• Duration is often the deciding factor. PTSD (>1 month) vs. acute stress disorder (3 days–1 month); persistent depressive disorder (≥2 years) vs. a single major depressive episode; schizophrenia's 6-month/1-month active-symptom requirement.

• Ego-syntonic vs. ego-dystonic sorts personality disorders from almost everything else. If a vignette describes a patient who doesn't see their own behavior as a problem, think personality disorder; if the patient is distressed by their own symptoms, think almost any other category.

• Watch for disorders that sound similar but aren't in the same category. OCD (Obsessive-Compulsive and Related Disorders) vs. OCPD (a Cluster C personality disorder); dissociative identity disorder (an identity/memory disorder) vs. schizophrenia (a psychotic disorder) — DID does not involve delusions or hallucinations by definition.

Common MCAT Mistakes

• Sorting schizophrenia symptoms by how severe they seem, rather than by whether they're added to normal behavior (positive) or missing from it (negative).

• Diagnosing bipolar I vs. bipolar II by how intense the mood episode feels, rather than by which specific episode type is present — a full manic episode (bipolar I) vs. hypomania plus a major depressive episode (bipolar II).

• Treating OCD and OCPD as the same disorder because of the similar names, rather than recognizing OCD as ego-dystonic and often acquired later in life vs. OCPD as ego-syntonic and a lifelong personality pattern.

• Assuming a patient who doesn't see their own behavior as a problem can't have a psychological disorder, rather than recognizing this as the defining, ego-syntonic feature of personality disorders.

MCAT-Style Concept Check

Question: A patient reports recurrent, unexpected episodes of intense fear accompanied by trembling, sweating, and a sense of impending doom. These episodes occur without any identifiable trigger, and between episodes the patient reports persistent worry about having another one. Which disorder best fits this presentation?

• A) Generalized anxiety disorder

• B) Specific phobia

• C) Panic disorder

• D) Agoraphobia

Answer: C

Explanation: Recurrent, unexpected attacks marked by fear, trembling, sweating, and a sense of impending doom are the hallmark of panic disorder. The absence of an identifiable trigger rules out specific phobia (anxiety tied to a specific object or situation) and agoraphobia (anxiety tied to being somewhere escape might be difficult). Generalized anxiety disorder involves persistent worry about many different things rather than a pattern of discrete, sudden attacks.

FAQ

What's the difference between positive and negative symptoms of schizophrenia?

Positive symptoms are things added to normal experience — delusions, hallucinations, disorganized thought or behavior, and catatonia. Negative symptoms are things missing from normal experience — flat or blunted affect and avolition (decreased motivation).

What's the difference between bipolar I and bipolar II disorder?

Bipolar I requires a full manic episode, with or without major depressive episodes. Bipolar II requires hypomania plus at least one major depressive episode — a person with bipolar II never experiences a full manic episode by definition.

How is OCD different from OCPD?

OCD (obsessive-compulsive disorder) is ego-dystonic — the person is distressed by their own obsessions and compulsions and typically recognizes they're excessive. OCPD (obsessive-compulsive personality disorder) is ego-syntonic — the perfectionism and rigidity feel normal to the person, and it's a lifelong personality pattern rather than a specific, acquired set of obsessions and compulsions.

What does it mean for a disorder to be ego-syntonic vs. ego-dystonic?

Ego-syntonic means the individual perceives their own behavior as correct or in harmony with their goals — the defining feature of personality disorders. Ego-dystonic means the individual experiences the illness as intrusive and bothersome, which describes most other psychological disorders.