Basics Mental Illness Types, Symptoms, and Diagnosis By Amy Morin, LCSW Amy Morin, LCSW Facebook LinkedIn Twitter Amy Morin, LCSW, is a psychotherapist and international bestselling author. Her books, including "13 Things Mentally Strong People Don't Do," have been translated into more than 40 languages. Her TEDx talk, "The Secret of Becoming Mentally Strong," is one of the most viewed talks of all time. Learn about our editorial process Updated on February 17, 2021 Medically reviewed Verywell Mind articles are reviewed by board-certified physicians and mental healthcare professionals. Medical Reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by Steven Gans, MD Medically reviewed by Steven Gans, MD Steven Gans, MD is board-certified in psychiatry and is an active supervisor, teacher, and mentor at Massachusetts General Hospital. Learn about our Medical Review Board Print Verywell / Jessica Olah Table of Contents View All Table of Contents What Is Mental Illness? Prevalence Types Signs and Symptoms Causes Diagnosis Treatment Mental health conditions are disturbances in a person's thinking, feeling, or behavior (or a combination of these) that reflect a problem in mental function. They cause distress or disability in social, work, or family activities. Just as the phrase “physical illness” is used to describe a range of physical health problems, the term "mental illness" encompasses a variety of mental health conditions. Is Mental Illness Genetic? What the Research Says What Is Mental Illness? The American Psychiatric Association defines mental illness as a health condition that involves “changes in emotion, thinking, or behavior—or a combination of these.” If left untreated, mental illnesses can have a huge impact on daily living, including your ability to work, care for family, and relate and interact with others. Similar to having other medical conditions like diabetes or heart disease, there is no shame in having a mental illness, and support and treatment are available. Prevalence Mental illnesses are incredibly common in the United States. Each year: 1 in 5 U.S. adults experience mental illness1 in 25 U.S. adults live with serious mental illness1 in 6 U.S. youth aged 6 to 17 years experience a mental health illness Serious mental illness (SMI) is a term used by health professionals to describe the most severe mental health conditions. These illnesses significantly interfere with or limit one or more major life activities. Two of the most common SMIs are bipolar disorder and schizophrenia. Types There are hundreds of mental illnesses listed in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), the American Psychiatric Association’s diagnostic manual. The DSM-5 puts illnesses into categories based on their diagnostic criteria. Anxiety Disorders This group of mental illnesses is characterized by significant feelings of anxiety or fear, accompanied by physical symptoms such as shortness of breath, rapid heartbeat, and dizziness. Three major anxiety disorders are: Generalized anxiety disorder (GAD) Panic disorder Social anxiety disorder (SAD) Bipolar and Related Disorders Formerly known as manic depression, bipolar disorders are characterized by alternating episodes of mania, hypomania, and major depression. There are three broad types of bipolar disorder: Bipolar I Bipolar II Cyclothymia How Mania Varies Between the Bipolar Types Depressive Disorders The common feature of all depressive disorders is the presence of sad, empty, or irritable mood, accompanied by physical symptoms and cognitive changes that significantly affect a person's capacity to function. Examples include major depressive disorder and premenstrual dysphoric disorder (PMDD). Disruptive, Impulse-Control, and Conduct Disorders A group of psychiatric conditions that involve problems with the self-control of emotions and behaviors. Disorders in this group include: Intermittent explosive disorder Kleptomania Oppositional defiant disorder (ODD) Pyromania Dissociative Disorders This group of psychiatric syndromes is characterized by an involuntary disconnection between consciousness, memories, emotions, perceptions, and behaviors—even one's own identity or sense of self. Elimination Disorders Children with elimination disorders repeatedly void urine or feces at inappropriate times and in inappropriate places, whether the action is involuntary or not. Feeding and Eating Disorders Eating disturbances are characterized by a persistent disturbance of eating patterns that leads to poor physical and psychological health. Three major eating disorders include: Anorexia nervosa Binge-eating disorder Bulimia nervosa Gender Dysphoria Formerly known as gender identity disorder, gender dysphoria occurs when a person feels extreme discomfort or distress because their gender identity is at odds with the gender they were assigned at birth. Neurocognitive Disorders These disorders are characterized by a decrease in a person's previous level of cognitive function. In addition to Alzheimer's disease, other conditions in this category include: Huntington's diseaseNeurocognitive issues due to HIV infectionTraumatic brain injury (TBI) Medication or Substance-Induced Neurocognitive Disorder Neurodevelopmental Disorders These disorders typically manifest early in development, often before a child enters grade school. They are characterized by impairments of personal, social, academic, or occupational functioning. Examples of neurodevelopmental disorders include: Attention-deficit/hyperactivity disorder (ADHD)AutismLearning and intellectual disabilities Obsessive-Compulsive and Related Disorders As the name suggests, these disorders are characterized by the presence of obsessions and/or compulsions. Examples obsessive-compulsive and related disorders include: Body dysmorphic disorder Hoarding disorder Obsessive-compulsive disorder (OCD) Paraphilic Disorders Describes intense or persistent sexual interests that cause distress or impairment. These may involve recurrent fantasies, urges, or behaviors involving atypical sexual interests. Personality Disorders These disorders are characterized by an enduring inflexible pattern of experience and behavior that causes distress or impairment. There are currently 10 recognized personality disorders. Schizophrenia Spectrum and Other Psychotic Disorders These disorders are defined by abnormalities in one or more of the following areas: Delusions Disorganized thinking Disorganized or abnormal motor behavior Hallucinations Negative symptoms Sexual Dysfunctions This heterogeneous group of disorders is characterized by a person's inability to fully engage in or experience sexual pleasure. Some of the most common sexual dysfunctions include: Delayed ejaculation Erectile disorder Female orgasmic disorder Female sexual interest/arousal disorder Sleep-Wake Disorders There are several different types of sleep-wake disorders, and all involve problems falling asleep or staying awake at desired or socially appropriate times. These disorders are characterized by misalignment of circadian rhythms with the surrounding environment or abnormalities of the circadian system itself. Common sleep-wake disorders include insomnia and narcolepsy. Somatic Symptom and Related Disorders People with these disorders feel extreme, exaggerated anxiety about physical symptoms—such as pain, weakness, or shortness of breath. This preoccupation is so intense that it disrupts the person's daily life. Substance-Related and Addictive Disorders All substance-related disorders are characterized by a cluster of behavioral and physical symptoms, which can include withdrawal, tolerance, and craving. Substance-related disorders can result from the use of 10 separate classes of drugs. Trauma and Stressor-Related Disorders This group includes disorders that were related to exposure to a traumatic or stressful event. The most common is post-traumatic stress disorder (PTSD). Signs and Symptoms Everyone experiences peaks and valleys in their mental health. A stressful experience, such as the loss of a loved one, might temporarily diminish your psychological well-being. In general, in order to meet the criteria for mental illness, your symptoms must cause significant distress or interfere with your social, occupational, or educational functioning and last for a defined period of time. Each disorder has its own set of symptoms that can vary greatly in severity, but common signs of mental illness in adults and adolescents can include: Excessive fear or uneasiness: Feeling afraid, anxious, nervous, or panickedMood changes: Deep sadness, inability to express joy, indifference to situations, feelings of hopelessness, laughter at inappropriate times for no apparent reason, or thoughts of suicideProblems thinking: Inability to concentrate or problems with memory, thoughts, or speech that are hard to explainSleep or appetite changes: Sleeping and eating dramatically more or less than usual; noticeable and rapid weight gain or lossWithdrawal: Sitting and doing nothing for long periods of time or dropping out of previously enjoyed activities It's important to note that the presence of one or two of these signs alone doesn't mean that you have a mental illness. But it does indicate that you may need further evaluation. If you're experiencing several of these symptoms at one time and they're preventing you from going about your daily life, you should contact a physician or mental health professional. Causes There is no single cause of mental illness. Instead, it’s thought that they stem from a wide range of factors (sometimes in combination). The following are some factors that may influence whether someone develops a mental illness: Biology: Brain chemistry plays a major role in mental illnesses. Changes and imbalance in neurotransmitters, the chemical messengers within the brain, are often associated with mental disorders.Environmental exposures: Children exposed to certain substances in utero may be at higher risk of developing mental illness. For example, if your mother drank alcohol, used drugs, or was exposed to harmful chemicals or toxins when she was pregnant with you, you may be at increased risk.Genetics: Experts have long recognized that many mental illnesses tend to run in families, suggesting a genetic component. People who have a relative with a mental illness—such as autism, bipolar disorder, major depression, and schizophrenia—may be at a higher risk of developing it, for example.Life experiences: The stressful life events you’ve experienced may contribute to the development of mental illness. For example, enduring traumatic events might cause a condition like PTSD, while repeated changes in primary caregivers in childhood may influence the development of an attachment disorder. Diagnosis Diagnosis of a mental illness is a multi-step process that may include more than one healthcare provider, often starting with your primary care physician. Physical Exam Before a diagnosis is made, you may need to undergo a physical exam to rule out a physical condition. Some mental illnesses, such as depression and anxiety, can have physical causes. Thyroid problems and other physical diseases can also sometimes be misdiagnosed as mental health disorders due to overlapping or similar symptoms; this is why a thorough physical exam is essential. Your doctor will take a lengthy history and may order lab tests to rule out physical issues that could be causing your symptoms. If your doctor doesn't find a physical cause for your symptoms, you'll likely be referred to a mental health professional so you can be evaluated for mental illness. Is There a Blood Test for Depression? Psychological Evaluation A mental health professional, such as a psychiatrist or psychologist, will ask you a series of questions related to your symptoms and family history. They may even ask one of your family members to participate in the interview so they can describe the symptoms they see. Sometimes, the mental health professional will administer tests and other psychological evaluation tools to pinpoint your exact diagnosis or help determine the severity of your illness. Most psychiatrists and psychologists use the APA's Diagnostic and Statistical Manual of Mental Disorders (DSM) to diagnose mental health illnesses. This manual contains descriptions and symptoms for all of the different mental illnesses. It also lists criteria like what symptoms must be present, how many, and for how long (along with conditions that should not be present) in order to qualify for a particular diagnosis. This is known as the diagnostic criteria. It's not uncommon to be diagnosed with more than one mental illness. Some conditions increase the risk of other disorders. For instance, sometimes an anxiety disorder can develop into a depressive disorder. The Difference Between Provisional and Differential Diagnoses Treatment Most mental illnesses aren’t considered "curable," but they are definitely treatable. Treatment for mental health disorders varies greatly depending on your individual diagnosis and the severity of your symptoms, and results can vary greatly on the individual level. Some mental illnesses respond well to medications. Other conditions respond best to talk therapy. Some research also supports the use of complementary and alternative therapies for certain conditions. Often, treatment plans will include a combination of treatment options and will require some trial and error before finding what works best for you. A Word From Verywell Living with mental illness, whether it affects you or a loved one, can be very hard—but help is available. If you suspect that you or someone you love may have a mental illness, talk to your doctor, who may refer you to a mental health professional for further assessment, evaluation, and treatment. You can also reach out directly to a psychotherapist. If you or a loved one are struggling with mental health, contact the Substance Abuse and Mental Health Services Administration (SAMHSA) National Helpline at 1-800-662-4357 for information on support and treatment facilities in your area. For more mental health resources, see our National Helpline Database. How to Choose the Right Therapist for You 5 Sources Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. American Psychiatric Associations. What Is mental illness? Substance Abuse and Mental Health Services Administration. Key substance use and mental health indicators in the United States: Results from the 2018 National Survey on Drug Use and Health (HHS Publication No. PEP19-5068, NSDUH Series H-54). Rockville, MD: Center for Behavioral Health Statistics and Quality, Substance Abuse and Mental Health Services Administration. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 5th ed. American Psychiatric Association; 2013. American Psychiatric Association. Warning signs of mental illness. Uher R, Zwicker A. Etiology in psychiatry: Embracing the reality of poly-gene-environmental causation of mental illness. World Psychiatry. 2017;16(2):121-129. doi:10.1002/wps.20436 By Amy Morin, LCSW Amy Morin, LCSW, is a psychotherapist and international bestselling author. Her books, including "13 Things Mentally Strong People Don't Do," have been translated into more than 40 languages. Her TEDx talk, "The Secret of Becoming Mentally Strong," is one of the most viewed talks of all time. See Our Editorial Process Meet Our Review Board Share Feedback Was this page helpful? Thanks for your feedback! What is your feedback? Other Helpful Report an Error Submit Speak to a Therapist Online Advertiser Disclosure × The offers that appear in this table are from partnerships from which Verywell Mind receives compensation.