February 25, 2015

expert reaction to violence and depression

Writing in the Lancet Psychiatry, researchers have published their results of an analysis of a possible link between depression and violent crime in Sweden. They report that people with depressive symptoms were three times more likely to commit violent offences than those who had not been diagnosed with depression, and suggest that their results should be taken into account in clinical guidelines.

Prof. Shirley Reynolds, Director of the University of Reading’s Charlie Waller Institute for Evidence-Based Psychological Treatment, said:

“This is an impressive study but we need to be extremely cautious about how we interpret the results.  The study shows that very, very, few depressed people are convicted of violent crimes.  Depressed people are more at risk of harming themselves than they are of harming anyone else.

“Misusing these results could increase the stigma associated with depression and other mental health problems, and the compassion we feel for the millions of people who have depression.

“It is also important to understand that this study shows an association between convictions and depression. Depression doesn’t cause convictions, convictions don’t cause depression. Many other factors can explain the association. These include previous traumatic experiences, including violence towards the self, poverty and social deprivation, and poor care as a child. The researchers in this study have done a very good job of controlling for some of these – but this can only ever be partially successful.

“Crucially, the study also showed that depressed people were more likely to be convicted of violent crimes. But this study does not show that depressed people committed more crimes. It means they were caught and found guilty more often than people who were not depressed. They may have committed fewer crimes or the same number of crimes. We just don’t know and these data can’t tell us.

“How is it possible that depressed people are convicted more often if they may not have committed more crime? Depression is associated with low motivation, hopelessness and apathy, sadness and feelings of guilt. It is more common in those who have lower incomes, are unemployed and are excluded from mainstream society. Therefore people who are depressed may be less motivated to avoid punishment, more hopeless and may feel that they deserve to be punished and are therefore less likely to try to avoid being caught.

“Second, when accused of a violent crime, depressed people may also be more likely to be charged of that crime.  On average people who are depressed may make less effort to avoid punishment, and/ or may more readily admit to having committed an offence. Depression is also more common in those with lower incomes, less education and those who are unemployed. All of these things make it harder to get good legal advice and support and increase the change of being charged with an offence.

“Third, because they have less access to legal advice depressed people may also be more likely to be found guilty.   Their low mood and lack of energy and motivation, their own guilt and expectation of punishment may add to the chance that a judge or jury will find them guilty.

“Finally, depressed people, may even be more likely to admit to offences which they did not commit because they feel guilty and deserving of punishment, and/ or they are more susceptible to pressure to confess.

“Despite these caveats this is an important piece of research. However it is imperative that we treat the results with care.”

Prof. Joe Herbert, Emeritus Professor of Neuroscience, John van Geest Centre for Brain Repair, University of Cambridge, said:

“The paper is a very careful study of a large subject database, under comparatively carefully controlled and defined conditions. However, before we jump to the conclusion that ‘depression causes violent crime’ or even that ‘having depression makes committing violent crime more likely’ (i.e. depressed people are an increased danger to society) we need to consider the following caveats.

“It is not clear from the data that the subjects were depressed or recovered at the time they committed crimes. So is it a history of depression or the presence of depression that they studied?

“The average age of onset (around 30 years) suggests to me that they missed a considerable number whose actual first episode was during adolescence: so many will have been recurrent depression. Depression during adolescence (common) can have adverse effects on education, achievement, social function etc. all of which could predispose to anti-social behavior.

“They studied only out-patient referrals. If Sweden resembles the UK, most depression is treated by GPs (i.e. first level referrals). So they are studying a selected population.

“As they discuss, they have no information on the treatment their subjects had, or were, undergoing. So is it depression or the treatment that is responsible? (or neither).

“They show that other factors – abuse, drugs, alcohol etc. – had huge effects compared to depression. Since all these are linked, despite their statistical attempts to separate them we must wonder whether there is a pattern of behavior here in those who commit violent crime, rather than a single factor.

“They present no information on lifestyle, particularly the advent of aversive life events which commonly precede the onset of depression. These events may have their own contribution to anti-social behavior.

“All these provisos make drawing a direct link between depression and violent crime very uncertain and over-simple. Finally, it is clear that depression itself is not a single illness, but there is no information on whether subtypes might be specifically linked to violence.”

‘Depression and violence: a Swedish population study’ by Fazel et al. will be published in The Lancet Psychiatry at 00:01 UK time on Wednesday 25^th February, which is also when the embargo will lift. 

Declared interests

None declared