The idea of a possible link between testosterone and depression is not a new one: testosterone has long been associated with changes in mood and changes in appetite, and for several decades scientists have been looking at whether the hormone could be useful for treating depression too.
With the new meta-analysis, covering 1,890 men in total, researchers from the Technische Universität (TU) Dresden institute in Germany wanted to try and find a definitive connection between testosterone treatments and the symptoms of depression.
"We wanted really to clear up the picture and try to find out what is really going on, and is testosterone something that might be one day interesting for clinicians for treatment of depressive disorders or not," one of the team, Andreas Walther from TU Dresden in Germany, told the Guardian.
What they found across the 27 placebo-controlled studies was that testosterone treatments were indeed associated with a "significant" reduction of depressive symptoms, especially when higher doses were given.
Before we start prescribing these treatments as a matter of course though, it's worth remembering that a meta-study like this covers a lot of different variables and scenarios – it's not quite as well-controlled as a single study managed by a single team.
For example, some of those 1,890 men had low testosterone levels, while others didn't; some were on antidepressants, while others weren't; and some had been diagnosed with a depressive disorder, while others only had symptoms.
Nevertheless, the results suggest that this link is something that's worth investigating further, the researchers say – adding that at the moment, testosterone is a rather controversial alternative to antidepressants.
Benefits and mood improvements were typically evident within the first six weeks, the meta-study concludes, and were noticeable in both younger and older men.
So while experts aren't recommending that all men with depression should start taking on testosterone supplements, they are saying more comprehensive studies should happen – particularly as alternative therapies are badly needed.
"This new study shows that testosterone may be helpful in some male patients," Michael Bloomfield from University College London in the UK, who wasn't involved in the study, told the Science Media Centre.
"However, we need more medical research to understand which patients might benefit from testosterone treatment and how this might fit in with existing treatments including medicines and psychotherapies."
Despite previous research into the topic, we're still lacking a large-scale, long-term study of how testosterone might affect men (and women) with depression. Based on this latest paper, such a study might well be worth the time and effort.
With both depression and suicide rates on the rise, it's more urgent than ever that new treatments are found for the condition. It's estimated that antidepressants can be effective in only up to 60 percent of cases, so alternatives are certainly required – and testosterone could be supplied relatively quickly if it was cleared for prescription.
According to Allan Young from King's College London in the UK, who wasn't involved in the latest study, the meta-analysis clearly shows a "a signal of benefit for depression in men", but he also says we should proceed carefully.
"With testosterone, there might be an effect on what one might think of broadly as vitality," Young told the Guardian. "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."
The research has been published in Jama Psychiatry.