Over the counter painkillers and anti-inflammatory drugs purchased at pharmacies could be effective treatments for depression.

The findings were made in a recent study that marked the largest meta-analysis ever conducted on the subject, Aarhus University reported. The World Health Organization (WHO) has estimated depression is one of the top five factors in loss of quality of life. 

The analysis looked at 14 international studies encompassing 6,262 patients who struggled with either depression or individual symptoms of the condition.

"The meta-analysis supports this correlation and also demonstrates that anti-inflammatory medication in combination with antidepressants can have an effect on the treatment of depression. When combined they give an important result which, in the long term, strengthens the possibility of being able to provide the individual patient with more personalized treatment options," said graduate student Ole Köhler, who is first author of the scientific article and a member of the research group from Aarhus University.

The large analysis allowed the researchers to be more certain of the link between anti-inflammatory drugs and depression than ever before. The researchers still need to weight the benefits that come along with these drugs with their possible risks and side effects to determine if they are reasonable treatments for depression. 

"The biggest problem with depression is that we do not know the causes that trigger the condition in the individual patient. Some studies suggest that the choice of antidepressant medication can be guided by a blood sample that measures whether there is an inflammatory condition in the body. Other studies show that the same blood samples could be used as a guideline on whether a depressive patient can be treated with anti-inflammatory drugs that works better when there is inflammation present simultaneously with the depression," Köhler said.

The researchers stressed the meta-analysis could not determine whether or not an inflammatory state was the only explanation for depression, but should be seen as a "significant milestone" in research on the subject.

The findings were published in a recent edition of the journal JAMA Psychiatry.