Types of mental illness

Different types of mental illness affect a person's thinking, emotional state and behaviours.

What is a mental illness?

Mental illness is a general term that refers to a group of illnesses that significantly affects how a person feels, thinks, behaves, and interacts with other people.

Mental illnesses can be very difficult and debilitating to those experiencing them, as well as their families and friends. They can also be be permanent, temporary, or come and go.

If you need to talk to someone about mental illness or a crisis in your life, please consider calling Lifeline on 13 11 14, beyondblue on 1300 22 4636, or the Kids Helpline on 1800 55 1800.

Types of mental illnesses

Bipolar disorder

Bipolar disorder (formerly know as manic depression), causes extreme mood swings including emotional highs (mania) as well as extreme lows (depression). These mood swings come in ‘cycles’ which can last days, weeks or even months (Better Health).

When episodes are extreme, some people may experience suicidal thoughts and symptoms of psychosis. A person may be affected so much that they are unable to distinguish reality from fantasy (Better Health).

The causes of bipolar disorder are not fully understood but are likely to be a combination of genetics and other causes.

Find out more:

Myths about bipolar disorder
Blog: Peter’s story about living with bipolar disorder


Depression is a mental illness which significantly affects the way someone feels, causing a persistent lowering of their mood and feelings of dejection and loss.

Depression has a variety of symptoms and will affect everyone in different ways. Some of the symptoms may include feeling extremely sad, disturbed sleep, loss of interest and motivation, feeling worthless, loss of pleasure in activities, anxiety, changes in appetite or weight, physical aches and pains, and impaired concentration.

While the exact cause of depression isn’t known, it is generally due to a combination of recent events, personal factors, family history, drug and alcohol use, as well as changes within the brain itself.

Find out more:

Myths about depression
Physical symptoms you didn’t know depression could cause

Anxiety disorders

People with anxiety disorders frequently have intense, excessive, and persistent worry and fear about everyday situations. These feelings interfere with daily activities, are difficult to control, are out of proportion to the actual danger, and can last a long time (Mayo Clinic).

Examples of anxiety disorders include generalised anxiety disorder, social anxiety disorder (social phobia) and specific phobias (Mayo Clinic).

Other symptoms of anxiety disorders can include panic attacks, trembling, sweating, difficulty breathing, feeling faint, rapid heartbeat, nausea, or avoiding certain situations.

Some of the causes or triggers of anxiety include the environment, stressful situations, trauma, family history, and substance abuse.

Find out more:

Myths about anxiety
Facts about panic attacks


Schizophrenia is a mental illness which influences the way a person thinks, feels, and acts, often distorting their perception of reality. It is a myth that those with schizophrenia have a ‘split personality’ – they have one just like everyone else.

If not receiving treatment, people with schizophrenia may experience persistent symptoms of psychosis.

They can have hallucinations such as seeing things, hearing voices, smelling odours, and feeling sensations on the skin. They can also have delusions which are false beliefs that strongly persist in their mind, and refuse to go away.

Other signs and symptoms can include low motivation, dulled emotions, rambling and disorganised speech, lack of desire to form social relationships, and a lack of ability to express emotion.

Find out more:

Myths about schizophrenia

Anorexia nervosa

Anorexia nervosa is an eating disorder characterised by an abnormally low body weight, an extreme fear of gaining weight, and a distorted perception of body weight. It can affect both men and women.

People who have anorexia can restrict their eating, compulsively exercise, and misuse laxatives or diet aids. It’s important to know that this behaviour is not connected to vanity or a lifestyle choice in any way.

Anorexia has one of the highest mortality rates of all mental illnesses, with 10-20% of people dying within 20 years from complications or suicide.

Find out more:

Myths about eating disorders

Bulimia nervosa

Bulimia Nervosa is a serious mental illness which involves binge-eating (consuming abnormally large amounts of food), followed by compensatory behavior such as vomiting, over exercising, fasting, or misuse of laxatives.

The cycle of binge eating and purging/exercising, leads to intense feelings of guilt and shame for the person. This mental illness often goes undetected because those with bulimia are normal weight or slightly overweight, and they often hide the behaviours associated.

Find out more:

Myths about eating disorders

Obsessive compulsive disorder (OCD)

Obsessive compulsive disorder (OCD) is an anxiety disorder where a person will experience thoughts and fears (obsessions) that lead to repetitive behaviours (compulsions). People with OCD are usually aware of the unreasonable nature of their obsessions and compulsions, however, feel unable to control it.

Some common obsessions include:

  • Fear of germs, dirt, and poisons
  • Fear of harm to yourself or others
  • Excessive concern with symmetry and orderliness
  • Hoarding, or saving and collecting things

Some common compulsions can include:

  • Excessive checking of items associated with safety such as locks and appliances
  • Excessive cleaning, washing, and showering
  • Touching, tapping or moving in a particular way or a number of times
  • Repeating words or numbers a certain number of times

Find out more:

Myths about OCD

Post-traumatic stress disorder (PTSD)

Post-traumatic stress disorder (PTSD) can develop after someone experiences or witnesses a traumatic event which threatened their life or safety, or that of others around them. For example, events which can trigger PTSD include a physical or sexual assault, an accident, natural disasters, or war.

Someone with PTSD may experience feelings of intense fear, panic, helplessness, or horror. They can re-live the traumatic event and feel intense emotional or physical reactions when reminded of the event such as sweating and heart palpitations.

Other symptoms include sleeping difficulties, lack of concentration, being easily startled, being constantly on the look out for danger, avoiding reminders of the event, and feeling emotionally numb.

Find out more:

Myths about PTSD

Impulse control disorder (ICD) and addiction

Impulse control disorder (ICD) is a class of disorders characterised by impulsivity and being unable to resist temptation which may harm oneself or others.

For example, pyromania (deliberately starting fires), kleptomania (stealing), compulsive shopping, sexual compulsion (increased urge in sexual behavior and thoughts), and compulsive gambling are examples of impulse control disorders.

Addiction and substance abuse can be of a variety of legal and illegal substances such as alcohol, drugs, gambling, prescription medicines (pain killers or sedatives), inhalants such as household cleaners, and even internet usage. When someone becomes dependent, they can experience cravings or withdrawal symptoms when they stop.

Find out more:

Understanding addiction: 7 facts you need to know

Body dysmorphic disorder

Body dysmorphic disorder (BDD) is where people constantly worry about the way they look. They can believe that minor or non-existent ‘flaws’, are actually serious defects in their appearance. It is however not related to vanity.

These perceived flaws cause the person substantial distress, and this obsession impacts their daily life. People often obsess over their appearance and body image, repeatedly check the mirror, groom themselves obsessively, constantly diet, over exercise, and seek reassurance.

It’s not uncommon for people to seek out numerous cosmetic procedures to try to ‘fix’ the perceived flaws, but are never satisfied.

Find out more:

Myths about eating disorders