It's conditional on their situation. For instance, assume that my life is picture-perfect. I have a great girlfriend, enough money to pay for school, all A's, my parents are happy, everything is great. Yet I'm still depressed. Anti-depressants should do wonders for me. No behavioral therapy is needed, as my life is already fine. However, if anti-depressants make me content with deplorable living conditions then they certainly have a negative effect. In this case, behavioral therapy along with anti-depressants would be optimum.