Sure, for severe cases studies have shown that depression medication helps, but that is not what the parent said:

  ...to treat any malady of the mind, and they have been proven to be barely more effective than placebo treatments

Which is also shown by studies[1][2]

1: http://www.ncbi.nlm.nih.gov/pubmed/7945737

2: http://www.ncbi.nlm.nih.gov/pubmed/18303940