What kind of likelihood is there of sexual side effects from anti-depressants?

Depends on drug. Ssri's & snri's more than 30%. If you're talking about wellbutrin, (bupropion) less than 2%. If tricyclics, about 2% except for Imipramine and clomipramine, which are more than 30%. Mirtazepine is about 2%. This can range from loss of libido, to delayed orgasm, to complete inability to climax.