A systematic review into the safety of ketamine as a treatment for depression shows the risks of long-term treatment remain unclear.

Ketamine as a depression treatment has shown enormous promise but questions around safety remain.

A world-first systematic review into ketamine as a treatment for depression published in the prestigious Lancet Psychiatry journal shows the risks of the drug's long-term use are unclear.

There has been a lot of interest in using ketamine - often associated with party drugs - to treat clinical depression and a lot of studies report it to be highly effective.

But there are concerns clinicians already treating patients with the drug may be putting them at risk because of a lack of monitoring of long-term side effects.

"A lot is written about its efficacy but much less about its safety," said psychiatrist and researcher Professor Professor Colleen Loo at the Black Dog Institute.

"A single treatment has incredibly powerful effects; it can take people from being severely depressed to completely well in one day but often the effects might wear off over a few days, so what people are now doing, quite sensibly, is rather than giving one treatment they give multiple treatments to maintain the benefit," Prof Loo explained.

But as the research review suggests there is no evidence to support the safety of this treatment approach just yet.

"When you start looking at multiple treatments there might be a different set of side effects that you are looking at and that is exactly what the literature suggests," Professor Loo told AAP.

Led by researchers from UNSW Sydney and Black Dog Institute, the review examined all prior published studies of ketamine treatment for depression.

It found few effectively reported the safety of repeated doses or sustained use.

The results showed that despite acute side effects such as headache, dizziness and blurred vision commonly occurring after a single treatment of ketamine, not all studies actively monitored for or reported on them.

While an advocate of ketamine use for treating the severely depressed, Prof Loo says its crucial to first determine that potential side effects don't outweigh the benefits.

Previous studies have linked longer-term ketamine use to bladder inflammation, liver damage and memory impairment.

Prof Loo says future ketamine-related depression studies should focus on assessing the safety of repeated dosing regimes.

"We haven't yet worked out how to give ketamine with repeated treatments in a way that it is effective and safe. There are very complex issues of dosing that we need to work out," Prof Loo said.