I took 100 mg 5-htp, but unable to sleep last night. should i decrease dose to 50mg? i have anxiety and depressoon. no medication going on.

Anxiety/depression: You might want to have a visit with your doctor to find out if there might be some medical condition underlying your inability to sleep. Also, find out if 5-htp is the right supplement for you, rather than dosage being the issue. Working with a psychologist could help you to develop good anxiety management skills, which may improve your sleep.