Summary: One study says that NAC is no better than placebo at keeping people from becoming depressed again after it gets them better. But if you look at the key graph you’ll see why that’s only a statistical conclusion, not a final conclusion.
This study is from the same group in Australia that published the original trial of NAC versus placebo for bipolar depression. Note that in the first phase of this study, one sees again a substantial improvement on NAC. But in the second phase of the study, half of the NAC improvers were switched to placebo. All of these patients were continued on their other treatments (medication and non-medication), so one interpretation of the results is that NAC helped them get better, but their other treatments kept them better, so much so that you can’t see any further NAC impact after the initial improvement.
Here’s the graph.
There is another finding from this study that is worth attention, though.
Promoting manic symptoms?
Given that conventional antidepressants can induce manic symptoms, does NAC carry the same risk?
The authors report ” Nine participants had a manic episode during the maintenance phase: two (3.2%) in the placebo group and seven (11.9%) in the NAC group.” These numbers are very small, only 9 episodes total. But that’s pretty lopsided. Statistically it is almost “significant” ( P = .070.).
In my view this may be one of the most significant findings in this report. I can write off the lack of benefit, relative to placebo, as an effect of the continued treatments the patients were on before the study began. But it’s crucial that we know whether NAC carries any degree of risk of making things worse, as antidepressants can do. Here we have a hint that the answer is yes (which makes sense to me, sorry to say, as I’ve seen NAC make a patient worse on three separate occasions).