Mental illness is a general term for a group of illnesses that may include symptoms that can affect a person’s thinking, perceptions, mood or behaviour. Mental illness can make it difficult for someone to cope with work, relationships and other demands.

There are many different conditions that are recognized as mental illnesses. The more common types include:

Anxiety disorders

People with anxiety disorders respond to certain objects or situations with fear and dread, as well as with physical signs of anxiety or panic, such as a rapid heartbeat and sweating. An anxiety disorder is diagnosed if the person’s response is not appropriate for the situation, if the person cannot control the response, or if 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 feeling overly happy, or fluctuations from extreme happiness to extreme sadness. The most common mood disorders are depression, bipolar disorder, and cyclothymic disorder.

Psychotic disorders

Psychotic disorders involve distorted awareness and thinking. Two of the most common symptoms of psychotic disorders are hallucinations — the experience of images or sounds that are not real, such as hearing voices — and delusions, which are false fixed beliefs that the ill person accepts as true, despite evidence to the contrary. Schizophrenia is an example of a psychotic disorder.

Eating disorders

Eating disorders involve extreme emotions, attitudes, and behaviours involving weight and food. Anorexia nervosa, bulimia nervosa, and binge eating disorder are the most common eating disorders.

Impulse control and addiction disorders

People with impulse control disorders are unable to resist urges, or impulses, to perform acts that could be harmful to themselves or others. Pyromania (starting fires), kleptomania (stealing), and compulsive gambling are examples of impulse control disorders. Alcohol and drugs are common objects of addictions. Often, people with these disorders become so involved with the objects of their addiction that they begin to ignore responsibilities and relationships.

Personality disorders

People with personality disorders have extreme and inflexible personality traits that are distressing to the person and/or cause problems in work, school, or social relationships. In addition, the person’s patterns of thinking and behaviour significantly differ from the expectations of society 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 plagued by constant thoughts or fears that cause them to perform certain rituals or routines. The disturbing thoughts are called obsessions, and the rituals are called compulsions. An example is a person with an unreasonable fear of germs who constantly washes their hands.

Post-traumatic stress disorder (PTSD)

PTSD is a condition that can develop following a traumatic and/or terrifying event, such as a sexual or physical assault, the unexpected death of a loved one, or a natural disaster. People with PTSD often have lasting and frightening thoughts and memories of the event, and tend to be emotionally numb.