insomnia
"My pain specialist recommended this and after reading reviews I was so reluctant to take it, however I tried it and yes it did work 20mins later. I found myself relaxed, it was like I took a valium but when I woke up my heart rate was so low which wasn't normal for me. My HR is usually 65-80 but when I woke up I had a irregular heart beat of 43bpm. I thought I was going to have a panic attack cos of a sunken feeling in my chest. 
I suffer with PTSD, depression, anxiety and have CRPS so I do take 8 meds when necessary. Will I continue taking 2mg melatonin? No, unless the blood test shows ur "lacking melatonin" I wouldn't recommend this. The number of complaints is quite alarming to me."