St John's doesn't interfere with anti-depressants - it actually increases their effectiveness which can be a bad thing. If they are SSRIs - you are on taking it with St John's may cause serotonin syndrome which may include symptoms of agitation, confusion, hallucinations, shivering, tachycardia (increased heart beat) and tremor.

The SSRIs (Selective Serotonin Re-uptake Inhibitors) stop serotonin being taken up so they remain in circulation longer giving the anti-depressant effect.

Those in Queensland (and S.A. too I think) can access a natural supplement through their naturopath called 5HTP - which is an amino acid call tryptophan which is converted to serotonin in the body. Its an anti-depressant and also controls cravings etc.
http://www.womenshealthsupplements.com/en/featured_products/Happy_Sense_60.html

Tryptophan used to be widely use:
Tryptophan is a natural amino acid that's found there (among other foods). Yet we've been told that l-tryptophan is toxic. Originally it was available, very cheaply, in any HF store. Then an episode occurred wherein a (single) manufacturer tried a shortcut that caused a toxic problem from contamination. It was evident, however, from early on, that any trouble from tryptophan was traceable back to this one company.

Tryptophan had been used for years, in very high doses, with no ill effects (prescription drugs should be so lucky!).

Unfortunately, the syndrome caused by the contaminant was, in some cases, serious. All tryptophan was pulled from the market (not an illogical reaction at the very beginning). Once the problem was tracked down, however, the FDA never returned tryptophan to its normal commercial status. For a long time it was completely unavailable. Now, at least, it can be acquired by prescription only, as if it's some controlled substance.

Tryptophan is involved in the formation of serotonin, and that's significant. Serotonin is needed for proper sleep patterns, control of depression, and even the ability to relax adequately. Properly applied doses of l-tryptophan were amazingly useful, both for insomnia and anxiety. At one time it became such a multi-million-dollar sales item that it was negatively impacting the sale of prescription drugs for the same symptoms. There are those, in fact, who believe the conspiracy against tryptophan was due to this fact (and I'm one of 'em). Even psychiatric professionals were using the stuff since you couldn't kill yourself with it as could be done with some prescriptions.

Anyway, now that good ol' tryptophan is by prescription only (and far more expensive because of it), the public has to turn to one of its relatives for a reasonably priced solution to insomnia and anxiety. Instead of tryptophan we have 5-hydroxytryptophan, or 5-HTP. This substance can perform the same functions as tryptophan and actually tends to do it in lower doses. I still prefer the original since 5-HTP costs a bit more than tryptophan originally did and is handled just slightly differently from its precursor, but with Big Brother taking care of us, I guess that's the way it goes.

All in all, 5-HTP can be worth a try if insomnia or anxiety is a problem. Ask your doc, of course, since anything that alters mood should be monitored, and especially if you're on a prescription for a similar symptom.
http://www.chelationtherapyonline.com/articles/p83.htm

amazing what our plants can give us to help us.

I have tried it on its own when I wasn't on anti-depressants but it didn't work for me.

If it reacts with anti-depressants and you need to be diognosed by a doctor then who would ever use it? doctors are not really known to prescribe natural alternatives when there is an effective drug to take. Its a pitty more people are not in a position to take the nateral alternative and see if it would help them