There are many various conditions which might be recognized as mental illnesses. The commonest types include:
- Anxiety disorders: People with anxiety disorders react to certain objects or situations with fear and terror and show physical signs of hysteria or panic, similar to racing heartbeat and sweating. An anxiety disorder is diagnosed when the person's response is just not appropriate to the situation, when the person cannot control the response, or when the anxiety interferes with normal functioning. Anxiety disorders include generalized anxiety disorder, panic disorder, social anxiety disorder, and specific phobias.
- Mood disorders: These disorders, also called affective disorders, involve persistent feelings of sadness or periods of excessive happiness or fluctuations between extreme happiness and extreme sadness. The commonest mood disorders are depression, bipolar disorder and cyclothymia.
- Psychotic disorders: Psychotic disorders involve distorted consciousness and considering. Two of probably the most common symptoms of psychotic disorders are hallucinations – experiencing images or sounds that aren't real, similar to hearing voices – and delusions, that are false, fixed beliefs that the person with the disorder assumes to be true despite evidence on the contrary. Schizophrenia is an example of a psychotic disorder.
- Eating disorders: Eating disorders involve extreme feelings, attitudes, and behaviors related to weight and food. Anorexia nervosa, bulimia nervosa, and binge eating disorder are probably the most common eating disorders.
- Impulse control and addiction disorders: People with impulse control disorders cannot resist the urge or impulse to perform actions that would harm themselves or others. Examples of impulse control disorders include pyromania (setting fires), kleptomania (theft), and compulsive gambling. Alcohol and medicines are common objects of addiction. People with these disorders often turn out to be so preoccupied with the objects of their addiction that they start to neglect responsibilities and relationships.
- Personality disorders: People with personality disorders have extreme and inflexible personality traits which might be distressing to the person and/or cause problems at work, school, or social relationships. In addition, the person's thought and behavior patterns differ significantly from society's expectations and are so rigid that they interfere with the person's normal functioning. Examples include antisocial personality disorder, obsessive-compulsive personality disorder, histrionic personality disorder, schizoid personality disorder, and paranoid personality disorder.
- Obsessive Compulsive Disorder (OCD): People with OCD are affected by constant thoughts or fears that cause them to perform certain rituals or routines. The intrusive thoughts are called obsessions, and the rituals are called compulsions. An example is an individual with an unfounded fear of germs who continually washes their hands.
- Posttraumatic stress disorder (PTSD): PTSD is a condition that may occur after a traumatic and/or terrifying event, similar to a sexual or physical assault, the unexpected death of a loved one, or a natural disaster. People with PTSD often have persistent and frightening thoughts and memories of the event and are inclined to be emotionally numb.
Other, less common kinds of mental illnesses include:
- Stress response syndromes (formerly called adjustment disorders): Stress response syndromes occur when an individual develops emotional or behavioral symptoms in response to a stressful event or situation. Stressors may include natural disasters similar to earthquakes or tornadoes, events or crises similar to a automotive accident or diagnosis of a serious illness, or interpersonal problems similar to divorce, the death of a loved one, job loss, or a drug problem. Stress response syndromes typically begin inside three months of the event or situation and end inside six months after the stressor ceases or is eliminated.
- Dissociative disorders: People with these disorders suffer from severe disturbances or alterations in memory, consciousness, identity, and general perception of themselves and their surroundings. These disorders are often related to overwhelming stress, which stands out as the results of traumatic events, accidents, or disasters that the affected person has experienced or witnessed. Dissociative identity disorder, formerly called multiple personality disorder or “split personality,” and depersonalization disorder are examples of dissociative disorders.
- Artificial disturbances: Factitious disorders are conditions through which an individual consciously and intentionally induces or complains about physical and/or mental symptoms with a purpose to put himself within the role of a patient or someone in need of help.
- Sexual and gender-specific disorders: These include disorders that affect sexual desire, sexual performance, and sexual behavior. Sexual dysfunction, gender identity disorders, and paraphilias are examples of sexual and gender-specific disorders.
- Somatization disorders: In somatization disorder (formerly also called psychosomatic disorder or somatoform disorder), an individual experiences physical symptoms of illness or pain with excessive and disproportionate suffering, no matter whether or not a health care provider can discover a medical cause for the symptoms.
- Tic disorders: People with tic disorders make sounds or exhibit random body movements which might be repetitive, rapid, sudden, and/or uncontrollable. (Involuntary sounds are called vocal tics.) Tourette syndrome is an example of a tic disorder.
Other diseases or conditions, including various sleep disorders and lots of types of dementia, including Alzheimer's disease, are sometimes classified as mental illnesses because they affect the brain.