The most significant side effects and adverse reactions may occur with long-term use (many months or longer). Administration of 5-HTP alone depletes catecholamines (dopamine, norepinephrine, and epinephrine).12,15 When dopamine depletion is great enough, 5-HTP will no longer function.15 If other centrally acting monoamine-related disease processes involving catecholamines are present, administration of 5-HTP alone may deplete dopamine, norepinephrine and epinephrine thereby exacerbating these conditions.15
"5HTP has helped me manage my anxiety and after years of PTSD related nightmares, I'm finally sleeping properly. It's helped massively with suicidal ideation, even during better times the intrusive thoughts were always lurking. For the first 7-10 days I did have quite noticeable side effects, headaches, feeling nauseous and shaking a little but I continued to take it as TBH it was better than side effects of prescribed anti depressants I've experienced in the past , which is probably not the most sensible but now I'm happy I did. I take this with a combination of L-tyrosine and B vitamins and magnesium. Probably also worth mentioning is the ease I've managed to sort out my binge eating, I've lost 13kg in the last 4 months which has been a fantastic thing for me and now my BMI is back in the healthy range."
For Anxiety: "I am a 32 year old female with anxiety and HTP5 works great for me. It slows down my thought spirals and I don't have a racing heart anymore. One tablet in the morning and one late afternoon, the calming effect lasts all day. I've never felt sick or nauseous from it, but I do get very vivid dreams. Fortunately I wake up very calm. I'm so glad I tried this."
Generally, efficacy studies related to 5-HTP fall into one of two categories: open (nonblinded) and double-blind, placebo-controlled studies. One naturopathic physician, who is considered by some to be a 5-HTP expert,17 interprets the results from an open study on his web site as follows:18 He reported one of his more impressive studies that involved 99 patients who were described as suffering from therapy resistant depression. These patients had not responded to any previous therapy including all available antidepressant drugs as well as electro convulsive therapy. Specifically reported was, “These therapy resistant patients received 5-HTP at dosages averaging 200 mg daily but ranging from 50 to 600 mg per day. Complete recovery was seen in 43 of the 99.”18