I wouldn't go that far, but there are many studies that have looked at the genetic (biological) basis for brain function/behavior [0]. Once you're at the level of gene expression, which some of those studies go into, you're at a level of acetylation, methylation, etc., which is easily categorized as chemistry.

The bigger argument I get into with coworkers is the blurry line between brain function/behavior stuff and psychology.

[0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3030621/