Comment by PaulKeeble

Trials are really different skill set compared to the scanning for these chemicals or in this case meta studying. Trials involve large numbers of people you have determined do and do not have the condition you are trying to treat and then having your treatment and having some way to measure if the treatment is impacting the thing you expect it to (brain choline levels) and whether that impacts the symptoms (anxiety).

Trials cost millions and in this case would require a number of different expertise, meta studies on the other hand is just reading and statistical analysis with knowledge of the biases of papers and assessing them critically and they don't cost millions.