I've had a delayed sleep schedule since I was in my teens. Never had a diagnosis but I'm pretty confident it was DSPS. I used a combo of a powerful stimulant in the morning (caffeine + Adderall) and powerful sedative at night (mirtazapine, quetiapine, benzo, countless others, but mirtazapine is one of the strongest drugs I have ever taken, for anything, and I have taken from every class of psychotropic drug) to keep myself functioning according to social standards (primarily school at that age).
I figure that because my sleep schedule was aligned to a different time I wasn't actually getting any quality sleep in my drug-induced sleep states. Now I am finding it is possible sometimes to force sleep with drugs BUT if the sleep does not line up with where your circadian rhythm is it is very non-restorative. Things keep getting odder though.
Eventually after several crashes it was no longer possible to take stimulants without getting immediately sick. I reverted to around 5 am bedtime. At that point it was regular DPSP. I was, 20, maybe? I am 26 now.
(Trust me I know stimulants are bad. If I could take back the years of stimulant use and abuse I would do it because they were responsibility for some of the worst crashes that I never fully recovered from, and I'm pretty sure they hastened the course of my illness. I might even have recovered like some young people afflicted with ME do, but I clobbered any chance of recovery with drugs to push myself to try and complete school.)
Now in the last 2-3 years it has transformed into non-24. And very recently it has gone completely off the rails and doesn't seem like a schedule at all (random naps, exhaustion sleeps, sleep from sedatives [wired-but-tired but forced to sleep sleep], all different qualities and at no set time).
Currently I am decoupling all sleep from mirtazapine as the absurd half-life on this drug ensures you are "locked" in bed in an extremely uncomfortable mental state. This happens if you take it and it doesn't put you to sleep, which happened to me after years of use.
As it stands it appears all efforts to correct sleep schedule backfire. For example I have tried many times to "push forward". I do this because trying to go to bed earlier to fit a normal rhythm, never, ever, works. All the sleep hygiene stuff (with the exception of light, which I found to be true) is baby stuff and doesn't work. What I have tried instead is to push forward, like chronotherapy. This doesn't seem to work either though. I will stay in the correct schedule for 1, maybe 2 days, but it's gone by the 3rd. My body strongly rejects the "corrected" schedule and moves forward until it reaches some absurd but slightly later date every day (like non-24). This can lead to weird things like double sleeps, or no sleep at all for 24 or more hours. All in all manipulating my schedule has been a complete disaster.
Now I think it is going to that stage past non-24 where there isn't actually a rhythm at all. If I understand correctly in non-24 you still have a rhythm, it just pushes forward by some number of minutes every day. I feel like now there is no rhythm.
Honestly no idea what to do.
It messes with how I feel about myself the most. And it shapes other people's perceptions about me.
If I had to give some advice it would be that forcing sleep with drugs could backfire in the long run. It did for me but hey we are all individual chemistry.