Get the facts on common mental disorders, such as those related to anxiety, attention deficit, conduct, depression, schizophrenia, and trauma.
The following are descriptions of the most common categories of mental illness in the United States.
Anxiety disorders are characterized by excessive fear or anxiety that is difficult to control and negatively and substantially impacts daily functioning. Fear refers to the emotional response to a real or perceived threat while anxiety is the anticipation of a future threat. These disorders can range from specific fears (called phobias), such as the fear of flying or public speaking, to more generalized feelings of worry and tension. Anxiety disorders typically develop in childhood and persist to adulthood. Specific anxiety disorders include generalized anxiety disorder (GAD), panic disorder, separation anxiety disorder, and social anxiety disorder (social phobia).
National prevalence data indicate that nearly 40 million people in the United States (18%) experience an anxiety disorder in any given year. According to SAMHSA’s report, Behavioral Health, United States – 2012, lifetime phobias and generalized anxiety disorders are the most prevalent among adolescents between the ages of 13 and 18 and have the earliest median age of first onset, around age 6. Phobias and generalized anxiety usually first appear around age 11, and they are the most prevalent anxiety disorders in adults.
Evidence suggests that many anxiety disorders may be caused by a combination of genetics, biology, and environmental factors. Adverse childhood experiences may also contribute to risk for developing anxiety disorders.
For information about the treatment of anxiety disorders, visit SAMHSA’s Treatments for Mental Disorders page. Find more information about anxiety disorders on the National Institute of Mental Health (NIMH) website.
Attention deficit hyperactivity disorder (ADHD) is defined by a persistent pattern of inattention (for example, difficulty keeping focus) and/or hyperactivity-impulsivity (for example, difficulty controlling behavior, excessive and inappropriate motor activity). Children with ADHD have difficulty performing well in school, interacting with other children, and following through on tasks. Adults with ADHD are often extremely distractible and have significant difficulties with organization. There are three sub-types of the disorder:
- Predominantly hyperactive/impulsive
- Predominantly inattentive
- Combined hyperactive/inattentive
ADHD is one of the more common mental disorders diagnosed among children. Data from the 2011 National Health Interview Survey (NHIS) indicate that parents of 8.4% of children aged 3 to 17 years had been informed that their child had ADHD. For youth ages 13 to 18, the prevalence rate is 9%. The disorder occurs four times as often among boys than girls. It is estimated that the prevalence of ADHD among adults is 2.5%.
Current research suggests that ADHD has a high degree of heritability, however, the exact gene or constellation of genes that give rise to the disorder are not known. Environmental risk factors may include low birth weight, smoking and alcohol use during pregnancy, exposure to lead, and history of child maltreatment.
The three overarching features of ADHD include inattention, hyperactivity, and impulsivity. Inattentive children may have trouble paying close attention to details, make careless mistakes in schoolwork, are easily distracted, have difficulty following through on tasks, such as homework assignments, or quickly become bored with a task. Hyperactivity may be defined by fidgeting or squirming, excessive talking, running about, or difficulty sitting still. Finally, impulsive children may be impatient, may blurt out answers to questions prematurely, have trouble waiting their turn, may frequently interrupt conversations, or intrude on others’ activities.
People with bipolar and related disorders experience atypical, dramatic swings in mood, and activity levels that go from periods of feeling intensely happy, irritable, and impulsive to periods of intense sadness and feelings of hopelessness. Individuals with this disorder experience discrete mood episodes, characterized as either a:
- Manic episode—abnormally elevated, expansive, or irritable mood accompanied by increased energy or activity that substantially impairs functioning
- Hypomanic episode—similar to a manic episode, however not severe enough to cause serious social or occupational problems
- Major depressive episode—persistent depressed mood or loss of interest or pleasure
- Mixed state—includes symptoms of both a manic episode and a major depressive episode
People exhibiting these symptoms are most frequently identified as having one of two types of bipolar disorders: bipolar I disorder or bipolar II disorder. The bipolar I diagnosis is used when there has been at least one manic episode in a person’s life. The bipolar II diagnosis is used when there has been a more regular occurrence of depressive episodes along with a hypomanic episode, but not a full-blown manic episode. Cyclothymic disorder, or cyclothymia, is a diagnosis used for a mild form of bipolar disorder.
The combined prevalence of bipolar I disorder, bipolar II disorder and cyclothymia is estimated at 2.6% of the U.S. adult population and 11.2% for 13 to 18 year olds.
A family history of bipolar disorder is the strongest risk factor for the condition, and the level of risk increases with the degree of kinship.
As mentioned previously, bipolar disorders are characterized by manic and depressive episodes. In children, manic episodes may present as an excessively silly or joyful mood that is unusual for the child or an uncharacteristically irritable temperament and are accompanied by unusual behavioral changes, such as decreased need for sleep, risk-seeking behavior, and distractibility. Depressive episodes may present as a persistent, sad mood, feelings of worthlessness or guilt, and loss of interest in previously enjoyable activities. Behavioral changes associated with depressive episodes may include fatigue or loss of energy, gaining or losing a significant amount of weight, complaining about pain, or suicidal thoughts or plans.
Depressive disorders are among the most common mental health disorders in the United States. They are characterized by a sad, hopeless, empty, or irritable mood, and somatic and cognitive changes that significantly interfere with daily life. Major depressive disorder (MDD) is defined as having a depressed mood for most of the day and a marked loss of interest or pleasure, among other symptoms present nearly every day for at least a two-week period. In children and adolescents, MDD may manifest as an irritable rather than a sad disposition. Suicidal thoughts or plans can occur during an episode of major depression, which can require immediate attention (to be connected to a skilled, trained counselor at a local crisis center, people can call 1-800-272-TALK (8255) anytime 24/7).
Based on the 2014 NSDUH data, 6.6% of adults aged 18 or older had a major depressive episode (MDE) in 2014, which was defined by the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). The NSDUH data also show that the prevalence of MDE among adolescents aged 12 to 17 was 11.4% in 2014, while female youths were about three times as likely as male youths to experience a MDE.
MDD is thought to have many possible causes, including genetic, biological, and environmental factors. Adverse childhood experiences and stressful life experiences are known to contribute to risk for MDD. In addition, those with closely related family members (for example, parents or siblings) who are diagnosed with the disorder are at increased risk.
A diagnosis for MDD at a minimum requires that symptoms of depressed mood (for example, feelings of sadness, emptiness, hopelessness) and loss of interest or pleasure in activities are present. Additional symptoms may include significant weight loss or gain, insomnia or hypersomnia, feelings of restlessness, lethargy, feelings of worthlessness or excessive guilt, distractibility, and recurrent thoughts of death, including suicidal ideation. Symptoms must be present for at least two-weeks and cause significant impairment or dysfunction in daily life.
Disruptive, Impulse Control, and Conduct Disorders
This class of disorders is characterized by problems with self-control of emotions or behaviors that violate the rights of others and/or bring a person into conflict with societal norms or authority figures. Oppositional defiant disorder and conduct disorder are the most prominent of this class of disorders in children.
Oppositional Defiant Disorder
Children with oppositional defiant disorder (ODD) display a frequent and persistent pattern of angry or irritable mood, argumentative/defiant behavior, or vindictiveness. Symptoms are typically first seen in the preschool years, and often precede the development of conduct disorder.
The average prevalence of ODD is estimated at 3.3%, and occurs more often in boys than girls.
Children who experienced harsh, inconsistent, or neglectful child-rearing practices are at increased risk for developing ODD.
Symptoms of ODD include angry/irritable mood, argumentative/defiant behavior, or vindictiveness. A child with an angry/irritable mood may often lose their temper, be frequently resentful, or easily annoyed. Argumentative or defiant children are frequently combative with authority figures or adults and often refuse to comply with rules. They may also deliberately annoy others or blame others for their mistakes or misbehavior. These symptoms must be evident for at least six months and observed when interacting with at least one individual who is not a sibling.
Occurring in children and teens, conduct disorder is a persistent pattern of disruptive and violent behaviors that violate the basic rights of others or age-appropriate social norms or rules, and causes significant impairment in the child or family’s daily life.
An estimated 8.5% of children and youth meet criteria for conduct disorder at some point in their life. Prevalence increases from childhood to adolescence and is more common among males than females.
Conduct disorder may be preceded by temperamental risk factors, such as behavioral difficulties in infancy and below-average intelligence. Similar to ODD, environmental risk factors may include harsh or inconsistent child-rearing practices and/or child maltreatment. Parental criminality, frequent changes of caregivers, large family size, familial psychopathology, and early institutional living may also contribute to risk for developing the disorder. Community-level risk factors may include neighborhood exposure to violence, peer rejection, and association with a delinquent peer group. Children with a parent or sibling with conduct disorder or other behavioral health disorders (for example, ADHD, schizophrenia, severe alcohol use disorder) are more likely to develop the condition. Children with conduct disorder often present with other disorders as well, including ADHD, learning disorders, and depression.
The primary symptoms of conduct disorder include aggression to people and animals (for example, bullying or causing physical harm), destruction of property (for example, fire-setting), deceitfulness or theft (for example, breaking and entering), and serious violations of rules (for example, truancy, elopement). Symptoms must be present for 12 months and fall into one of three subtypes depending on the age at onset (childhood, adolescent, or unspecified).
Obsessive-Compulsive and Related Disorders
Obsessive-compulsive disorder (OCD) is defined by the presence of persistent thoughts, urges, or images that are intrusive and unwanted (obsessions), or repetitive and ritualistic behaviors that a person feels are necessary in order to control obsessions (compulsions). OCD tends to begin in childhood or adolescence, with most individuals being diagnosed by the age of 19.
In the United States, the 12-month prevalence rate of OCD is estimated at 1.2% or nearly 2.2 million American adults.
The causes of OCD are largely unknown, however there is some evidence that it runs in families and is associated with environmental risk factors, such as child maltreatment or traumatic childhood events.
Prerequisites for OCD include the presence of obsessions, compulsions, or both. Obsessions may include persistent thoughts (for example, of contamination), images (for example, of horrific scenes), or urges (for example, to jump from a window) and are perceived as unpleasant and involuntary. Compulsions include repetitive behaviors that the person is compelled to carry out ritualistically in response to an obsession or according to a rigid set of rules. Compulsions are carried out in an effort to prevent or reduce anxiety or distress, and yet are clearly excessive or unrealistic. A common example of an OCD symptom is a person who is obsessed with germs and feels compelled to wash their hands excessively. OCD symptoms are time-consuming and cause significant dysfunction in daily life.
Find more information about OCD on the NIMH website.
The defining characteristic of schizophrenia and other psychotic disorders is abnormalities in one or more of five domains: delusions, hallucinations, disorganized thinking, grossly disorganized or abnormal motor behavior, and negative symptoms, which include diminished emotional expression and a decrease in the ability to engage in self-initiated activities. Disorders in this category include schizotypal disorder, schizoaffective disorder, and schizophreniform disorder. The most common diagnosis in this category is schizophrenia.
Schizophrenia is a brain disorder that impacts the way a person thinks (often described as a “thought disorder”), and is characterized by a range of cognitive, behavioral, and emotional experiences that can include: delusions, hallucinations, disorganized thinking, and grossly disorganized or abnormal motor behavior. These symptoms are chronic and severe, significantly impairing occupational and social functioning.
The lifetime prevalence of schizophrenia is estimated to be about 1% of the population. Childhood-onset schizophrenia (defined as onset before age 13) is much rarer, affecting approximately 0.01% of children. Symptoms of schizophrenia typically manifest between the ages of 16 and 30.
While family history of psychosis is often not predictive of schizophrenia, genetic predisposition correlates to risk for developing the disease. Physiological factors, such as certain pregnancy and birth complications and environmental factors, such as season of birth (late winter/early spring) and growing up in an urban environment may be associated with increased risk for schizophrenia.
People with schizophrenia can experience what are termed positive or negative symptoms. Positive symptoms are psychotic behaviors including:
- Delusions of false and persistent beliefs that are not part of the individual’s culture. For example, people with schizophrenia may believe that their thoughts are being broadcast on the radio.
- Hallucinations that include hearing, seeing, smelling, or feeling things that others cannot. Most commonly, people with the disorder hear voices that talk to them or order them to do things.
- Disorganized speech that involves difficulty organizing thoughts, thought-blocking, and making up nonsensical words.
- Grossly disorganized or catatonic behavior.
Negative symptoms may include flat affect, disillusionment with daily life, isolating behavior, lack of motivation, and infrequent speaking, even when forced to interact. As with other forms of serious mental illness, schizophrenia is related to homelessness, involvement with the criminal justice system, and other negative outcomes.
Trauma- and Stressor-Related Disorders
The defining characteristic of trauma- and stressor-related disorders is previous exposure to a traumatic or stressful event. The most common disorder in this category is post-traumatic stress disorder (PTSD).
PTSD is characterized as the development of debilitating symptoms following exposure to a traumatic or dangerous event. These can include re-experiencing symptoms from an event, such as flashbacks or nightmares, avoidance symptoms, changing a personal routine to escape having to be reminded of an event, or being hyper-aroused (easily startled or tense) that makes daily tasks nearly impossible to complete. PTSD was first identified as a result of symptoms experienced by soldiers and those in war; however, other traumatic events, such as rape, child abuse, car accidents, and natural disasters have also been shown to give rise to PTSD.
It is estimated that more than 7.7 million people in the United States could be diagnosed as having a PTSD with women being more likely to have the disorder when compared to men.
Risk for PTSD is separated into three categories, including pre-traumatic, peri-traumatic, and posttraumatic factors.
- Pre-traumatic factors include childhood emotional problems by age 6, lower socioeconomic status, lower education, prior exposure to trauma, childhood adversity, lower intelligence, minority racial/ethnic status, and a family psychiatric history. Female gender and younger age at exposure may also contribute to pre-traumatic risk.
- Peri-traumatic factors include the severity of the trauma, perceived life threat, personal injury, interpersonal violence, and dissociation during the trauma that persists afterwards.
- Post-traumatic risk factors include negative appraisals, ineffective coping strategies, subsequent exposure to distressing reminders, subsequent adverse life events, and other trauma-related losses.
Diagnosis of PTSD must be preceded by exposure to actual or threatened death, serious injury, or violence. This may entail directly experiencing or witnessing the traumatic event, learning that the traumatic event occurred to a close family member or friend, or repeated exposure to distressing details of the traumatic event. Individuals diagnosed with PTSD experience intrusive symptoms (for example, recurrent upsetting dreams, flashbacks, distressing memories, intense psychological distress), avoidance of stimuli associated with the traumatic event, and negative changes in cognition and mood corresponding with the traumatic event (for example, dissociative amnesia, negative beliefs about oneself, persistent negative affect, feelings of detachment or estrangement). They also experience significant changes in arousal and reactivity associated with the traumatic events, such as hypervigilance, distractibility, exaggerated startle response, and irritable or self-destructive behavior.
For information about the treatment of PTSD, visit SAMHSA’s Treatments for Mental Disorders page. Find more information about PTSD on the NIMH website or on the National Center for PTSD maintained by the Department of Veterans Affairs.