As someone who
ingests both St John's wort and
alcohol every day in substantial quantities for the purpose of
feeling better, I can assure you alcohol does not cancel out its effect. Alcohol is indeed a
depressant, and I'm sure it reduces the
effectivity of the St John's wort somewhat, but the drug has utterly transformed my life and made me much happier, because I'm free of permanent
depression, and I don't particularly need to feel the effect of it on an alcohol-free lifestyle. I'm plenty
liberated as it is.
St John's wort also adversely interacts with warfarin for heart disease. It is unfortunate that some people can't have the advantage of it because of other drugs they're taking -- the Pill is a real bummer --; and like most such drugs it doesn't work for all people: works for something like 80% of people, which is similar to the figure for Prozac.
It is the drug of first choice for the condition known as mild to moderate depression, unless you are medically unable to take it. It is not so suitable for the condition known as major depression (clinical depression), though I doubt there's any harm trying. There have been no reports of people turning into suicidal axe murderers after a few.
My experience of photosensitivity (I'm the sort who can take a tan) is an unpleasant, disturbing tingling of my scalp when under bright lights (such as in a pub where there are lights everywhere). This went away after a few weeks or I got used to it. And even if I hadn't: I can have my scalp tingle or I can cry at night because I'm depressed... let me see now... how to choose, how to choose...
What it appears to do is block negative emotional memories from the amygdala, which otherwise would circulate in the cortex and become obsessive worries and fears. My experience has been that it almost entirely blocks imaginary anxieties. So it also happens to makes me more socially confident (I have social phobia).
It does not in any way stop real (i.e. well-founded) anxieties. If I have good cause to worry at a particular time about someone's health, or my love life, I do so just as strongly, and get quite as depressed as ever. That's not nice but it's there for a reason and I'm happy to have it.
For the record: I am an arch-rationalist, virulently opposed to alternative medicine rubbish, which I condemn as tap water, fraud, and gullibility. But St John's wort works. The effect is huge, far far stronger than can be put down to the placebo effect.
A further note. I recently read that, as with anything like Prozac, it takes two or three weeks before it has any effect. Does it. The first pill I ever had in my life produced a powerful effect in two and a half hours. Your milage may vary, but I find this timing consistently exact. If I haven't had one for more than half a day and I start slipping into mild depression, then after two hours and thirty minutes, plus or minus five minutes (truly: I've timed it on numerous occasions) it hits as a sudden slight warming, relaxing, a load off my mind, a very slight euphoria.
It's not a pep pill, it's not a stimulant, and it doesn't even make you happy as such, except in this sense: if you'd been a martyr to tinnitus or backache all your adult life, and you took a pill that made the tinnitus or backache go away, you'd be happy because it was gone. Depression isn't unhappiness, but it stops you being happy.
And I used to be afraid to be happy. An overabundance of positive neurotransmitters would subside and lead to a more pronounced unhappiness. This no longer happens.
Compulsory final warning, this is my personal experience, it might not be right for you.
After three years. You can get used to it, unfortunately. For the last six months or so I've felt I've not been getting any such effect from it as I used to: no warmth, no loss of worry. So I finally stopped taking it to try, and lack of it makes me more "nervous", but not more depressed. And taking a pill after abstinence no longer gives me the old effect back. *sigh*
But perhaps I'm being too hasty. I was expecting a sudden drop, and a single pill making a sudden change. After several weeks of not regularly using it, I've gone back to my three a day, and yes it is calming me, making me not worry much, and giving a general "Oh, blow it" attitude to things that had been more upsetting over the past couple of works. So I think I'll stay with it.