A person's attributional style is the way in which they ascribe causes to events in their lives. People who regard the causes of negative events as global, stable and internal (due to their own shortcomings) are more likely to develop depression. Some researchers believe that this negative attribution is itself a symptom of depression (mood-related) while others believe it is a permanent outlook (trait-related) that may be due to genetic factors. A study of 213 people in Cardiff compared depressed people and their siblings to a control group of unaffected people and their brothers and sisters. The researchers found that attributional style had more to do with current mood than trait-related factors. However, the tendency to blame oneself for negative events was related to having had a prior episode of depression suggesting that depression can have a 'scarring' effect predisposing people towards a negative view of events. People who had experienced minor difficulties were found to have a more positive attributional style suggesting that minor life events are protective against pessimistic attributions.
Ball, Harriet A., McGuffin, Peter and Farmer, Anne E. - Attributional style and depression British Journal of Psychiatry April 2008, 192(4), 275-278