Schizophrenia, Depression and a Glaring Gap in Knowledge
Depression is a frequently occurring symptom in schizophrenia. Some maintain that depression is a symptom of schizophrenia whilst others view it as a discrete mood disorder. Whatever the standpoint the importance of depression in schizophrenia is important for at least two reasons. First, anything that adds to the difficulties and discomfort of the individual needs to be addressed. Secondly, schizophrenia is recognized as having the highest suicide rate of any mental disorder. Despite refinements in treatment, suicide in schizophrenia seems to have remained stable at around 10-15 per cent (Roy, 1986). However, results from the National Comorbidity Study (1995) show individuals with schizophrenia and at least one lifetime comorbid mood disorder, have a 40.4 per cent chance of suicide or attempted suicide.
Estimates of the prevalence of depression in schizophrenia vary greatly (anything from 25-75 per cent). Depression is often associated with crisis and admission to hospital. Various theories also abound as to why people become depressed before, during or after an episode of psychosis. A depressive episode following a psychotic episode is understandable given the radical effect this may have on work, relationships, self-esteem and the sense of alienation that often follows.
Substance misuse, particularly alcohol, is a significant cause of depression. Long term use of cannabis is also known to cause depression as is cocaine, although this is less commonly used.
The role of antipsychotic medication as a possible cause of depression has been studied in earnest since the late 1960s. Because antipsychotic medicine acts directly on the neurotransmitter dopamine, known to have a major role in mood, a ‘pharmacogenic depression' was suggested. Over time, other theories have developed and have attracted some support, but the great weight of evidence seems to suggest that antipsychotics are responsible for relatively few cases of depression.
There seems little doubt that assessment and treatment of depressive symptoms in schizophrenia is clinically challenging. A systematic review of research literature gives an indication as to why this is probably the case. Whitehead et al (2002) sought out randomized clinical trials that compared antidepressant medication with placebo for people with schizophrenia or schizoaffective disorder who were also suffering from depression. Despite a search of international databases only eleven studies met the criteria. All were small, and randomized fewer than 30 people to each group. The authors concluded that literature in the area is of poor quality. There may be some evidence that antidepressants are beneficial but the authors are reserved due to what they regard as a likelihood of overestimating treatment effects, or at worst, selectively reporting statistics.
The fact that no convincing evidence exists to support or refute the use of antidepressants in treating people with schizophrenia is particularly disturbing in the light of what we know about the associated risk factors. Time surely for a properly designed study to answer the question - are antidepressants effective in the treatment of depression in people with schizophrenia?
Mulholland, C., Cooper, S. (2000) The symptoms of depression in schizophrenia and its management. Advances in Psychiatric Treatment 6: 169-177.
Whitehead, C., Moss, S., Cardno, A., Lewis, G. (2002) Antidepressants for people with both schizophrenia and depression. Cochrane Database of Systematic Reviews 2002, Issue 2, Ant No: CD002305. DOI: 10. 1002/14651858.