In reply to Robyn Vacher:
Great question. It doesn't appear on the wada website, which surprises me. But it probably depends on why you are taking it.
If it's for depression, then you would expect it to improve mood and energy therefore improve running performance. If it was for anxiety and it had a really good affect on you (Mind it's serotonin not and NR or tricyclic) then in could decrease in terms of pace, maybe not enjoyment. Distance and tempo probably are factors.
What the research does say is if you take antidepressants and exercise together for depression the effects are over and above what each treatment does alone, so it's a great idea providing you have doctors clearance for other medical conditions. Also, cardiovascular exercise specifically is better at improving heart rate variability, which is a good inverse correlate for depression and anxiety, which might facilitate coming of the meds a bit quicker. Sereotonin has a very broad range of actions throughout the body, really versatile and complex receptors!