Is this dangerous? Will it cause serotonin syndrome or other complications? I dont have any physical health issues, and I'm very experienced with both drugs individually. I want to have a life changing trip, preferably one that doesnt give me brain damage.
Try a few months in India or South East Asia it will change your life and youll probably just get the shits - Sorry couldn't resist.
Seriously though it sums up what I will try to say - If your experienced you will already know life changing trips are not engineered they just happen, usually when you least expect it and usually not on massive amounts but in the right setting where it's the discovery of something you never thought of before suddenly presents itself and gives you that OMG moment.
No one can tell you when and how but from personal experience commonly the OMG moments don't occur when you simply up the dose or plan / continue to do the same thing / same setting. Mix it up a bit first before going large. Do something different whilst partaking.
I personally had a life changer after an all night rave on MDMA. Didn't feel like bed or the after party the sun was shining so I jumped on a bus and went to a place called Glastonbury. Managed to score and then climb up and sat on Glastonbury tor (a really weird very old man made hill with lots of mythology surrounding it) dropped what was supposedly a 150 ug blotter and OMG.
You already know that the dose you state ain't ridiculous dosage; if your experienced, your stuff is tested and you've got a strong head for psyches. But it is strong enough to put you seriously out there and can end up with the 'what's my name, where am I, what have I done' scenario, sometimes fun to experience if you got your shit together but also it can be very scary too and not necesarily life changing in the way I think you want. Although even my bad trips I consider good trips as they have all taught me something.
Seriously if you have not yet tried it - keep to a lower dose stick on LSD (don't mix) but go for a complete environment change. Somewhere of course which is still 'safe'
Seratonin syndrome at 200 mg I'd say very low risk. I don't know the exact process and someone should correct me if I'm wrong - I believe MDMA causes seratonin release and LSD doesn't.