I don’t think the observation that cancer contributes to depression would win any awards for profundity, it’s likely such news would put a crimp in anyone’s day. Indeed, the very fact that the news of cancer itself can influence our emotions  makes it difficult to examine the contributing factors toward depression in those suffering from cancer. Our ability to foresee our own possible demise and react emotionally to it confounds attempts to tease out the strands of cause and effect. Approximately 10% of cancer sufferers are diagnosed with clinical depression and up-to two thirds experience some sort of mood disorder.

In order to separate out the effect of conscious knowledge of the disease from the psychological symptoms researchers have to turn to rats. How do you tell if a rat is depressed? To find out the scientists monitored the rat’s Twitter and Facebook pages for negative statements, no actually the rats are subjected to a swimming test, the longer the rats floated in the water without trying to escape the more depressed the animal is. The researchers found that rats with cancer showed signs of depression but not other behaviours normally associated with sickness, implying the rats were not simply feeling unwell.

Analysis of the rats tumours, blood and brain showed an increase in specific cytokines that have been linked to behavioural changes. In other words the presence of the tumour triggers changes in the brain that influence behaviour. This means that depression could be considered another symptom of cancer and not merely a by-product of knowledge of the cancer. This could have implications for how we treat depression in cancer patients and help them deal with the side-effects, simply knowing that being depressed is not something under their own control might itself be helpful.