A new meta-analysis of 27 existing studies has concluded that testosterone treatment seems to be effective in reducing depressive symptoms in men. While a relationship between testosterone and depression has been hypothesized for many years, experts suggest more specific and rigorous trials are still needed.

Testosterone is an important hormone for both men and women. Some hypothesize that the prominence of testosterone in men is one of the reasons women tend to more frequently suffer from depression, osteoporosis and sleep problems. Any link between testosterone levels and depression still hasn't been confidently verified, and while a small body of evidence seems to be growing suggesting it could be a viable depression treatment, it still isn't recommended as a genuine therapy.

This new meta-study, from a small team of European researchers, gathered together data from 27 separate placebo-controlled trials, with the primary goal of examining whether testosterone helped reduce symptoms of male depression. The conclusions were relatively clear, finding those men who underwent testosterone treatment did display significant reductions in their depressive symptoms relative to the placebo cohorts.

Interestingly, the meta-study also revealed some other secondary observations. Greater efficacy dealing with depressive symptoms was identified in cohorts receiving higher doses of the hormone, while there was also no relationship found between a man's initial levels of testosterone and depression, importantly suggesting that low testosterone levels are not necessarily a significant risk factor for the condition.

Joe Herbert, from the University of Cambridge, didn't work on this new study but suggests that the research affirms the need for a clear and rigorous trial to specifically explore the efficacy of testosterone treatment for male depression.

"This is a very careful analysis, and it has considerable implications," says Herbert. "However, it does point to the need for a properly constituted trial of testosterone (previous ones have often been too small, or not well carried out)."

An editorial accompanying the research, published in the journal JAMA Psychiatry, also cautions drawing any solid conclusions from this research. Although the editorial admits the meta-analysis is "well-performed," it reminds readers that larger, and longer-term doses of testosterone are generally not recommended due to potential adverse health effects.

"Furthermore, neither the long-term safety nor the efficacy of testosterone therapy has been established in any depressive disorder," the editorial concludes.

Of course, this new meta-study is not reaching a conclusion that hasn't been raised before. A variety of anecdotal reports and case studies have suggested for many years that there may be a positive correlation between testosterone supplementation and the alleviation of depression. Allan Young, from King's College London, accepts that this association may be real, but suggests it is unclear exactly what testosterone could be doing to improve a person's sense of well-being.

"With testosterone, there might be an effect on what one might think of broadly as vitality – men might feel like they have got more energy, might eat more, but that may not be accompanied by an effect on core symptoms of depression such as low mood and loss of interest," Young explains to The Guardian.

Nevertheless, most experts do agree that larger and more specific trials are certainly warranted to better explore the relationship between testosterone and mood. We still do not know the long-term safety profile or ideal dosage, and even more broadly whether this works as a depression treatment for women as effectively as it may for men.

The new meta-study was published in the journal JAMA Psychiatry.