- Blue is naturally calming. Good choice especially given the theme. I don't know how I feel about the flowers. I think they are kind of busy but they also are hidden well enough to not be a huge problem.
- Medicines/therapies could likely be combined and renamed, "Treatments," or something similar. I'd also probably add a disclaimer somewhere on the site that it's not ran by licensed counselors/psychologists/doctors/psychiatrists and it's designated as more of a support group to avoid any misconceptions. This is more of a "cover your butt" suggestion.
- The forum descriptions are long, large, and hard to see. I'd consider reducing the font size to at least be slightly smaller than the forum names. I'd also consider a slightly different shade of blue. Finally, I'd correct the grammatical structure. Way too many capital letters. "I Mean That The First Letter Of Most Words in The Descriptions Are Capitalized and This Makes It Hard to Read."
- As someone with a Master's Degree in Special Education - Autism, I have to point out that Autism is not classed as an anxiety disorder. Even though a large percentage of individuals with autism also experience anxiety, the two are not synonymous nor is Autism under the anxiety umbrella. I'd consider separating the two forums. There is a lot more to Autism Spectrum Disorders than anxiety.
As Abi mentioned, nice domain name. TalkMH.com is easy to remember. I'd work to build your SEO so that search engines relate MH to mental health.