my own experience is that antidepressants have no effect on me for anxiety (and ive taken lots of them over a long period of time ) the only non benzo that does anything for me is lyrica (pregabalin ) , that said lots of people reckon AD's help them.
a lot of psychiatric drugs are known to not work well in people with autism (they either do very little or cause lots of side effects in even small dosages ) - unfortunately it all comes down to trial and error and they affect each person differently (if you look at the side effects listed on most drugs (AD's ) these day they list just about everything they can think off - including 'may cause depression' ) .