News · Brain & Mental Health
Ketamine beat a sedative comparison by 7 points in bipolar depression that had resisted two treatments
Ketamine's antidepressant effect is established in ordinary depression and largely untested in bipolar disorder, where the fear is tipping someone into mania. A trial of 68 patients looked for both.
- Depression scores fell further on ketamine than on the comparison drug.
- No one in either group developed mania, hypomania or psychosis.
- The comparison was an active sedative, not a saline placebo.
- Everyone stayed on a mood stabilizer or antipsychotic throughout.
- 68 patients randomized at three sites, which is small for a psychiatric trial.
Bipolar depression is the part of the illness that takes up most of the time and gets the least of the attention.
The manic episodes are what the diagnosis is built around and what emergency services see. But people with bipolar disorder spend far longer in the depressive phase, and the treatments that work well for ordinary depression are used cautiously here, because pushing someone out of depression can push them into mania instead.
That caution has left a gap. Ketamine has been studied extensively in major depression and hardly at all in this group.
What the trial did
Writing in JAMA Psychiatry, researchers ran the comparison at three sites in Ontario. Adults with bipolar I or II disorder in a moderate to severe depressive episode, who had already failed at least two proper medication trials, were randomized to four infusions over two weeks.
Half received ketamine. Half received midazolam, a sedative. Everyone stayed on their existing mood stabilizer or antipsychotic throughout.
The choice of comparison is the most important design decision in the study, and it is the reason the result carries weight.
Why the comparison drug matters so much
Ketamine does something noticeable while it is going in. People feel detached, dreamy, altered. Against salt water, everybody would know who got what within minutes, and a trial where participants can tell is barely a trial at all.
Midazolam produces a sedative experience without treating depression. It gives the comparison group something to feel, which is why it has become the standard active control in this field.
It worked imperfectly. After the first infusion, roughly half the participants correctly guessed their allocation, which is about what chance would produce but is not evidence that the blind held perfectly.
The result
Depression scores at two weeks were lower on ketamine, by a little over seven points on the scale used.
That is a moderate effect, and larger than several approved antidepressants manage against an active comparison. The plausible range around it is wide, stretching from a very large benefit down to a modest one, which is what 63 analyzed participants buys.
The safety question that prompted the caution
No cases of mania, hypomania, psychosis, or suicide attempts were observed in either group. One person in each group developed mixed features that fell short of hypomania.
This is the finding that will matter most to clinicians, and it needs the right amount of weight. A trial of this size can detect a common problem and cannot rule out an uncommon one. Seeing zero events in 68 people is reassuring about anything frequent and says little about anything rare.
What the illness is
Bipolar disorder is a mood disorder that can cause intense mood swings, between elevated or irritable states and depressive ones, sometimes with both together.
The reason the depressive side is undertreated is not neglect. It is that the safest antidepressant strategy in bipolar disorder has never been settled, and every option carries the risk of destabilizing the thing it is meant to treat.
Where it leaves the question
Further along than it was, and not at an answer.
Sixty-eight people at three sites is small. The follow-up ran to the end of a two-week course, so nothing here says how long the benefit lasts or what happens when infusions stop. Ketamine is also not a prescription someone fills; it is given intravenously under monitoring.
What the trial establishes is that the question is worth asking properly, in the group where the standard treatments have already failed and the alternatives are thin.
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What did the trial find?
Of 68 randomized participants (mean age 44.4 years; 55.8% female), 63 were included in the efficacy analysis. The mean Montgomery-Asberg Depression Rating Scale score at day 14 was significantly lower in the ketamine group than the midazolam group (between-group difference -7.3 points; 95% CI, -12.0 to -2.5; P = .003; Cohen d = 0.7). No cases of mania, hypomania, psychosis or suicide attempts were observed in either group.
Why compare against midazolam rather than salt water?
Because ketamine produces obvious effects during the infusion, so a saline placebo would be transparent to everyone. Midazolam is a sedative that feels like something without treating depression, which makes the comparison much harder to see through.
Did the blinding hold?
Partly. After the first infusion, 31 of 66 participants correctly guessed which treatment they had received, which is close to chance but not proof of perfect blinding. This is a known and largely unsolved problem in ketamine research.
What does treatment-resistant mean here?
Participants had a current moderate to severe depressive episode and had already failed at least two adequate trials of evidence-based medications. This is the group for whom the standard options have run out.
Why was mania the main safety concern?
Because antidepressant treatment in bipolar disorder can flip a person from depression into a manic or mixed state, which is why clinicians are cautious about using antidepressants there at all. The trial watched closely for it and saw none.
Is 7 points on the depression scale meaningful?
It is a moderate effect by the usual conventions, and larger than many approved antidepressants achieve against active comparisons. The plausible range around it is wide, running from a very large benefit to a modest one.
Does this mean ketamine should be used for bipolar depression?
One trial of 68 people does not establish a treatment. It is administered intravenously under monitoring in specialist settings, and the decision belongs with a psychiatrist who knows the person. This is general information rather than medical advice.