A diagnosis of depression is associated with a threefold increase in the risk of committing violent crime, an Oxford University study has found.
The study of nearly 50,000 people in Sweden found that 3.7% (641) of depressed men and 0.5% (152) of depressed women committed a violent crime after their depression diagnosis. This compares to 1.2% (4097) of men and 0.2% (1059) of women in the general population who had committed a violent crime.
'One important finding was that the vast majority of depressed persons were not convicted of violent crimes, and that the rates reported are below those for schizophrenia and bipolar disorder, and considerably lower than for alcohol or drug abuse,' said study author Professor Seena Fazel at the Department of Psychiatry at Oxford. 'Quite understandably, there is considerable concern about self-harm and suicide in depression. We demonstrate that the rates of violent crime are at least as high, but they don’t receive the same level of attention in clinical guidelines or mainstream clinical practice.'
The study, published in the journal The Lancet Psychiatry, takes advantage of a register maintained in Sweden, which connects every person born in in the country after 1932 to their parents.
The research team used this register and medical databases to track the medical records and conviction rates of 47,158 Swedish people diagnosed with depression. They compared these records to the records of 898,454 people matched for age and gender, but with no diagnosis of depression, following them up for an average of three years.
The researchers found that people who had been diagnosed with depression had a higher risk of both harm to others and self-harm: their risk for self-harm was 5-6 higher than the general population.
Compared to their siblings who did not have depression, depressed people were still twice as likely to be violent. The smaller difference in comparison to siblings versus the general population suggests that family-related factors – including shared genetic heritage and mistreatment during childhood – may contribute to the increased risk of violence by people with depression.
The study did not include people who had been hospitalized with depression, since hospitalization can be due to the threat of harm to others, which might elevate the level of risk calculated by the study. When researchers controlled for a previous history of violence, self-harm, psychosis, and substance misuse – all of which are known to increase an individual’s risk of violence, with or without depression – they still found an increased risk of violent crime among people with depression. However, the risk of violence when these factors were excluded was smaller, suggesting that risk of violence should be included in clinical risk assessments for people who have a previous history of violence, self-harm, psychosis, or substance misuse.
Violent crime and depression levels in Sweden are similar to other western countries, suggesting that the results may be broadly applicable in other countries.
The research was funded by the Wellcome Trust.