COMT, GAD, MAOA/B and addressing methylation too soon can definitely cause neuro-psych issues, but it all comes back to methyl pooling. SNPs in these genes can also contribute: ACE, DAO, MTHFR (e.g., A1298C). Homozygous or 'AA' results for COMT V158M is particularly associated with anxiety & startle response. Quite a few SNPs & quite a few medical conditions can contribute to anxiety, of course (e.g., gut health & bacteria resulting in toxin exposure).
For brain fog / concentration issues, follow up on SNPs affecting ammonia (such as NOS gene, etc.) & BH4 levels (DHPR gene, etc.), also.
With anxiety as a chief complaint, focus on magnesium, zinc, lithium, and B6 because if they're deficient, supplementation can have an immediately helpful impact. But that is a very broad generalization and you'll really have to be prepared to look at other nutrients, dietary needs, and conditions.