The two most widely used classification systems in psychiatry are the World Health Organisations ' International Classification of Disease and Related Health Problems ' (ICD) and the ' Diagnostic and Statistical Manual of Mental Disorders ' (DSM). Both the ICD and DSM provide a common language and standard criteria for the classisfication of mental disorders. Within the DSM are a group of diagnoses known as mood disorders. Some examples of mood disorders include Major Depressive Disorder (MDD) and Bipolar Disorder. The DSM states that ' The essential feature of MDD is a clinical course that is characterized by one or more Major Depressive Episodes without a history of manic, mixed or hypomanic episodes '. The DSM defines a Major Depressive Episode that of ' A period of at least two weeks during which there is either depressed mood or the loss of interest or pleasure in nearly all activities '. The DSM further states that individuals must also experience at least four additional symptoms drawn from the following list; ' Decreased energy or fatigue, feelings of worthlessness or guilt, difficulty thinking, concentrating or making decisions, changes in appetite (decreasing or increasing), weight (significant loss or gain), sleep (insomnia or hypersomnia) and or recurrent thoughts of death or suicidal ideation, plans or attempts '. Bipolar Disorder is defined as a ' Clinical course that is characterized by the occurance of one or more Manic Episodes '. It also states that individuals often experience 'One or more Major Depressive Episodes '. Bipolar Disorder is a recurrent disorder and more than 90% of individuals who have a single manic episode can go on to have future episodes. The ICD defines Bipolar Affective Disorder as a ' Combination of hypomanic, manic, mixed and depressive episodes'. Some other mood disorders defined within the DSM and ICD include Dysthymic Disorder, Cyclothymic Disorder and Substance - induced mood disorders. Another group of mental health...