Mental illness is defined as changes to an individual's behavior, emotional response, or thinking that lead to distress or problems functioning in social situations, work, or family life. Mental health issues are common, with millions of people affected each year. Experts estimate that 1 in 5 U.S. adults experience mental illness each year.

There are many different types of mental illnesses, ranging from anxiety and depressive disorders to obsessive-compulsive disorder (OCD) and post-traumatic stress disorder (PTSD). These mental disorders are diagnosed and treated based on criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) issued by the American Psychiatric Association.

This article will outline the most common mental health disorders in a comprehensive list.

What Causes Mental Illness?

There is no singular cause of mental illness. Instead, mental illness can usually be attributed to multiple factors, including brain chemistry, developmental experiences, and environmental causes.

Some common factors that have been linked to increased risk of mental illness include:

• Genetics: Mental illness tends to run in families. Research has shown that children of parents with mental illness are at increased risk of developing mental illness. However, genetics alone do not explain all the risks. Added environmental factors can make someone more susceptible. For example, genetic risk for major depression alone may not result in the development of major depression, but a traumatic event on top of genetic risk may make someone more susceptible. Epigenetics looks at how genes and the environment interact to cause mental illness.
• Physical environment: The environment in which a person lives also affects mental illness risk. Studies have shown that living in an urban area is a risk factor for mental illness. However, researchers note that urban environments may be a proxy for other underlying risk factors. For example, people living in urban environments may have greater exposures to pollutants or toxins or higher costs of living that lead to chronic stress.
• Social environment: Stressful life events can significantly impact mental health. Stressful life events vary widely, but significant personal conflicts, such as within an unhealthy relationship, are one example that has strong associations with anxiety and depression.

A Mental Illness List: Types of Mental Health Disorders

There are several different types of mental health disorders that each have a certain set of criteria. Details on each mental illness are found in the DSM-5, which healthcare providers and mental health professionals use to diagnose a mental health issue.

Mental health disorders can generally be grouped into categories. Some of the most common include:

• Anxiety disorders
• Eating disorders
• Mood disorders
• Personality disorders
• Trauma- and stressor-related disorders
• Psychotic disorders

Anxiety Disorders

Anxiety is generally characterized by feelings of tension, worrisome thoughts, and physical bodily sensations such as sweating or increased heart rate.

People who have an anxiety disorder often deal with recurring intrusive thoughts. Intrusive thoughts are unwanted, automatic thoughts that get stuck in your mind and cause great distress and anxious thinking, which can be extremely difficult to escape.

There are some major types of anxiety disorders:

• Generalized anxiety disorder (GAD): Chronic worry about a variety of concerns and other symptoms of anxiety often without a particular trigger
• Obsessive-compulsive disorder (OCD): Now in its own diagnostic category, this involves recurring, unwanted thoughts and repetitive behaviors (such as cleaning, hand washing, or tapping), often performed to try and alleviate the distress caused by the intrusive thoughts
• Panic disorder: Repeated episodes of intense fear or panic attacks, leading to physical symptoms such as chest pain, heart palpitations, and shortness of breath
• Social anxiety disorder (or social phobia): Overwhelming anxiety around social situations

Eating Disorders

An eating disorder is characterized by significant and persistent disturbances in eating behaviors and is often associated with unhealthy preoccupations with one's body. These disorders can potentially lead to serious medical consequences.

Though it is a mental health condition, it is also a physical one, since severe disturbances in eating patterns impact physical health. For example, severe restriction of calories, as is the case with anorexia nervosa, can cause a decrease in bone mineral density, increasing the risk of fractures.

There are several types of eating disorders:

• Anorexia nervosa: Intense fear of gaining weight or becoming fat, leading to self-starvation
• Bulimia nervosa: A cycle of binge-eating and purging behaviors such as self-induced throwing up
• Binge eating disorder: Eating a large amount of food in a short period of time, often accompanied with feelings of lack of control and shame
• Other specified feeding and eating disorders: Any other eating disorder that causes distress and impairs the ability to function at home or work
• Avoidant restrictive food intake disorder: A condition that is characterized by extremely picky eating that results in nutritional deficiencies
• Pica: Recurring episodes of eating of non-food objects, such chalk, metal coins, pebbles, or paper
• Rumination disorder: Repeatedly regurgitating food (bringing swallowed food back up), to rechew and re-swallow it

Mood Disorders

Mood disorders cover a variety of depressive and bipolar disorders. While everyone feels sad or depressed from time to time, a mood disorder is different. Mood disorders are very intense and persistent, and they significantly affect everyday life.

The following are the most common types of mood disorders:

• Major depressive disorder: Feeling sad, hopeless, losing interested in one's normal activities, along with other physical and mental symptoms that last two weeks or longer
• Persistent depressive disorder (formerly known as dysthymia): Chronic depressive symptoms that last two years or longer
• Bipolar disorder: A condition generally marked by alternating periods of depression and feelings of mania or elevated moods
• Substance-induced mood disorder: When alcohol, drugs, or medication causes depression or other mood disorder

Personality Disorders

Personality disorders are characterized by long-term maladaptive patterns of thought and behavior that may make it difficult to start or maintain relationships as well as deal with everyday stress in both personal and work life.

People with a personality disorder might not realize they have a mental illness.

There are many personality disorders, which can be classified into three major categories, each with its own set of personality disorders:

• Cluster A: Odd or eccentric behavior
• Schizoid personality disorder: Lifelong pattern of indifference toward others and social isolation
• Paranoid personality disorder: High degree of suspicion and mistrust of others without adequate cause
• Schizotypal personality disorder: A pattern of odd or eccentric behaviors and difficulty connecting in relationships
• Cluster B: Dramatic, emotional, or erratic behavior
• Antisocial personality disorder: Long-term pattern of manipulating or exploiting others without remorse
• Borderline personality disorder: Ongoing pattern of impulsive behavior, varying moods, unstable self-image, and problems with relationships
• Narcissistic personality disorder: Extreme sense of self-importance and lacking empathy for others
• Cluster C: Anxious fearful behavior
• Avoidant personality disorder: Extreme social inhibitions marked by fear of rejection and feelings of inadequacy
• Dependent personality disorder: Symptoms may include feelings of helplessness, submissiveness, or an inability to make simple decisions or take care of oneself
• Obsessive-compulsive personality disorder: Preoccupation with orderliness, rule-following, control, and perfection

Trauma- and Stressor-Related Disorders

Post-traumatic stress disorder (PTSD) is the central disorder in this category. It is a psychiatric disorder where a past traumatic experience, witnessed or experienced, causes severe distress and disruption to everyday living. A natural disaster, serious accident, war, rape, and sexual violence are examples of traumatic events that may lead to PTSD.

People with PTSD experience intense and disturbing thoughts and feelings that are related to the traumatic event, even if it happened a long time ago. They may avoid situations that might trigger a memory of the traumatic event or react strongly to ordinary things that bring them back to that traumatic time.

Post-traumatic stress disorders are sometimes differentiated into the following types, though they are not included in the DSM-5:

• Complex PTSD: PTSD that develops after prolonged, repeated trauma (such as long-term sexual or physical abuse) rather than an isolated traumatic event
• Delayed expression PTSD (formerly called delayed-onset PTSD): PTSD that develops more than six months after the trigger event
• Dissociative PTSD: Exhibition of prominent dissociation, or derealization and depersonalization, when recalling the traumatic experience

Psychotic Disorders

Psychotic disorders are mental illnesses that cause abnormal thoughts and perceptions that, in turn, cause someone to lose touch with reality.

Delusions and hallucinations are common. Psychotic disorders can cause great distress and functional challenges in everyday life.

Types of psychotic disorders include the following:

• Schizophrenia: Characterized by hallucinations, delusions, unusual behavior, and withdrawal
• Schizoaffective disorder: Combination of psychotic features such as delusions and mood symptoms like depression
• Schizophreniform disorder: Schizophrenia episode that lasts longer than one month but less than six months
• Delusional disorder: Experiencing delusions without the other symptoms or unusual behavior seen with schizophrenia
• Brief psychotic disorder: Short-term episode of psychosis lasting less than one month
• Substance-induced psychotic disorder: Psychosis causes by the short- or long-term effects of certain drugs such as LSD
• Psychotic disorder due to a medical condition

Diagnosis and Treatment for Mental Illness

Mental illness is generally diagnosed by a mental health professional, who uses the DSM-5 to evaluate whether someone meets the criteria for a certain mental illness. Sometimes it can take seeing more than one healthcare provider to make a formal diagnosis, and it often starts with talking with a primary care physician who can refer you to a mental health specialist.

Diagnosis may involve a medical evaluation to rule out any underlying physical causes that might be contributing to the mental illness. For example, a doctor may order bloodwork to rule out anemia or thyroid problems before diagnosing persistent depressive disorder. A psychiatrist or psychologist will ask about symptoms and family history and may use psychological evaluation tools, such as a questionnaire, to determine a diagnosis.

The good news: Mental illnesses are treatable and there are several treatment options for mental illness, with medication and psychotherapy being most common. Sometimes they are used in combination or it may be that just psychotherapy is needed. Psychotherapy can be particularly effective as it involves tools and techniques for combating unhelpful thoughts and behaviors that can help an individual cope long-term.

Summary

There are many types of mental illnesses, which range in severity and how they impact everyday life. There is no single cause for mental illness, and it is commonly caused by multiple factors, many of which are out of an individual’s control. Diagnosis requires a healthcare professional, who can also advise on treatment options.

A Word From Verywell

Mental illness still holds a lot of stigma. But the more that awareness of mental health increases, the more we are able to reduce the stigma around each individual's personal struggles and create more opportunity for everyone to get the help they need.

If you or someone you love are struggling with thoughts, behaviors, or emotional distress related to a mental illness, it can be scary and isolating. However, our hope is that by knowing more about the types of mental illnesses and having resources for learning more about them, you feel more empowered to reach out to a mental health professional, support group, or friend for help.

While mental illness can be caused by things out of your control, learning more about mental illness and seeking help doesn't have to be.