Mental disorders are illnesses that affect or are manifested in the brain.  They may impact on the way a person thinks, behaves, and interacts with other people.  The definition ‘mental disorder’ encompasses numerous psychiatric disorders that can vary in severity.

A mental disorder has a major impact on  a person’s wellbeing.  It may interfere directly with their daily functioning (at home, work and socially) and adversely affect quality of life.  Mental disorders are caused by a complex and poorly understood interaction between genetics, learned behavior, personality, past psychological influences, physical health, present situation and coping skills.  Mental disorders can have a physiological basis and arise from changes in brain chemistry.

The main characteristics of psychotic disorders are loss of insight and reality testing.  People with psychotic disorders experience delusions and hallucinations and do not understand these thoughts as abnormal.  The main psychotic disorders are schizophrenia, schizoaffective disorder and delusional disorders.  Schizophrenia is a serious mental disorder charactized by delusions, hallucinations, agitation, blunted affect, social withdrawal, apathy, anhedonia, and poverty of thought and content of speech.  In schizoaffective disorder, both affective illness and schizophrenia symptoms are seen.  The person’s premorbid adjustment is usually good; there is usually a sudden onset of illness after a specific stressor.  The prognosis of patients with schizoaffective disorders is better than that of patients with schizophrenia.  Delusional disorder, formerly known as paranoid disorder, is characterized by persistent nonbizarre delusions.

Mood disorders are clinical conditions characterized by a disturbance of mood or persistent emotional states that affect how a person acts, thinks and perceives his environment.  People with mood disorders often suffer from overwhelming feelings of sadness (depression), while others suffer from alternating periods of mania and depression (bipolar disorder).

Personality disorders are deeply ingrained, maladaptive patterns of behavior.  The initial signs of personality disorders can be recognized in adolescence or earlier and symptoms often continue throughout adult life.  Personality disorders can have an adverse effect both on the individual and on society.

Anxiety disorders include various combinations of mental and physical manifestations of anxiety not attributable to real danger and occurring either in attacks (panic disorder) or as a persisting state (generalized anxiety disorder).  Anxiety symptoms include emotional (fear), cognitive (anxious thoughts) and bodily symptoms (increased heart rate), the latter being caused by stimulation of the autonomic nervous system.  Anxiety disorders also include phobias, social phobia (social anxiety disorder), obsessive-compulsive disorder, and post-traumatic stress disorder.

Lundbeck Institute (n.d.).  Overview of mental disorders.  Retrieved May 5, 2013 from             http://www.brainexplorer.org/factsheets/psychiatry_overview.pdf