It's important to keep cortisol low, and over-exercise can cause cortisol to spike – as does depression in general, hence the sleeping difficulties many depressed people experience. Likely that's why resistance training and HIIT are more helpful in this case as there is less built up of stress hormones.

I've been diagnosed with moderate to severe depression, and I'm a trial runner and do CrossFit. It's a balancing act to find strength and feeling capable through sport without increasing insomnia and early waking, likely because of cortisol spikes.

Sport does more for me than antidepressants, which have little effect than making me feel tired all the time. I've gone through a whole battery of them with little success and I've become quite critical of them. But I'm lucky to generally like sport and eat pretty healthily; I can imagine for others that can be an extra stressor they really don't need.

Thanks this is new to me (I'm mostly a cardio guy), didnt' know there was any difference in sleep quality/duration between cardio and lifting. They both help sleep btw it just turns out according to recent research resistance training helps more. Both are need though for a healthy lifestyle and I think cardio is actually more accessible for most people; I'm gonna count brisk walking as cardio for most people and that's the most accessible type of excercise everyone but the extremely debilitated can do.

I don’t like anecdotal evidence, but for myself I was running regularly but still experiencing suboptimal sleep. I started resistance training again and my sleep immediately got better.

I'm down with that , resistance training is clearly good. Cardio is also clearly good (both groups had better sleep than the group that didn't do any cardio). People should just do something, even walking birskly. We should all simply try to move and/or lift things.