There is no single cause of suicide. However, more than 90 per cent of those who commit suicide have a mental disorder. People suffering from depression, schizophrenia, alcohol or other drug dependence are at greater risk. Social factors are also important, as shown in the historical fluctuations in the suicide rate. Unemployment and the blurring of traditional roles may be factors in the increased rate in young men. A small proportion of suicides are copy cat. Availability of firearms is a factor in male suicide.