Mental illness is widespread and often undiagnosed, with the World Health Organisation estimating that 450-million people worldwide suffer from mental illness.

So what is mental illness? It is "any diagnosable mental, behavioural, or emotional disorder that interferes with, or limits a person's ability to live, work, learn, and participate fully in his or her community," according to the US Substance Abuse and Mental Health Services Administration.

Over 200 kind of mental illness

There are over 200 kinds of mental illness. Among the most serious are psychotic disorders in which a person loses touch with reality, such as schizophrenia and other delusional disorders.

Schizophrenia affects about one percent of the population and usually manifests in males between the ages of 15 and 25 years, and in females between 25 and 35 years, according to Dr Yusuf Moosa, senior psychiatric specialist with Gauteng's Community Mental Health department.

Its symptoms include hallucinations (hearing voices and seeing visions), delusions (fixed, false beliefs) and bizarre or disorganised behaviour and or thoughts.

A less serious delusional disorder may involve an otherwise normal person holding one fixed delusion, such as a pathologically jealous man who is convinced his partner is unfaithful to him.

Mood disorders include depression and bipolar mood disorders. Depression can lead to suicide. Bipolar disorder (manic depression) is when a person fluctuates between being depressed and feeling very high or manic.

In the manic phase, the person's thoughts are rapid and tend to overwhelm them. They tend not to sleep and to have periods of rapid but non-productive activity. In this phase, the person may have grandiose delusions about possessing special powers, and are often very irritable. Bipolar disorder requires life-long therapy on mood stabilisers.

Disorders 'blur' into one another

"The diagnosis of mental illness is sometimes not clear cut, with some disorders 'blurring' into one another," says Moosa, who is also a senior lecturer in the psychiatric department at Wits University.

Personality disorders are often more difficult to manage. "Everyone is born with a temperament and this becomes their personality over time," says Moosa.

While most of us have some personality traits, these become disorders when they impact and become a problem for the people around them. It usually also affects the individuals social and occupational functioning.

Some examples of personality disorders:

• Paranoid: People who tend not to trust anyone.
• Schizoid: Withdrawn and asocial people who often relate better to animals than people.
• Histrionic: Melodramatic people who have frequent histrionics.
• Antisocial: Psychopaths who deceive, manipulate and have no concern for others.
• Borderline: Those for whom everything is seen in extremes of either good or bad.
• Narcissistic: They think they are the best.
• Dependent: People who cannot make any decisions on their own.
• Obsessive-compulsive: Those who are very meticulous and orderly about everything.

"Unfortunately," says Moosa, "many people do not seek psychiatric help because they don't want to be seen as 'crazy'. However, many mental illnesses can be treated with drugs that act on neurotransmitters in the brain and with psychological counselling".

Signs of mental illness

The outward signs of a mental illness are often behavioural. Individuals may be extremely quiet or withdrawn or may burst into tears or have outbursts of anger.

The following are signs that your loved one may want to speak to a medical or mental health professional:

In adults:

Pre-adolescents:

In younger children:

From the US National Mental Health Association and health-e.org.za