Fish oils (aka omega-3 long-chain polyunsaturated fatty acids, available from mackerel, salmon or cod liver) seem to have a particular effect on mood and behaviour, several studies have suggested. Depressed people with high omega-3 levels became less gloomy. University finals students were, perhaps surprisingly, less aggressive if they had been fed fish oil for three months. Manic depressives on fish oil felt better, too. Violent offences among young British prisoners fed fish oil fell by 40%. Some scientists suggest that the apparent rise in depression over the past century is not the result of people's greater willingness to admit to feeling bad, but is a real phenomenon connected to the fall in oily fish consumption.