Valerian and my liver

[capybara]

So I have occasional insomnia which from time to time makes my life very bad-- I HATE insomnia. So I discovered valerian a few years ago, which was a great improvement in quality of life-- I like the idea of it-- herbal, natural, non-addictive, yaddah yaddah. However a friend expressed concern about this, suggesting in as many words that my spleen might erupt out of my chest any second if I continued taking it. Now I've just read a tad on the kava thread about valerian being toxic. Does anyone know more about the negative effects of this stuff? Any herbalists by vocation? Input from medical physicians? Taken in reasonable doses (I take it perhaps once a week, usually less frequently than that, but some weeks more often, though) is this something to worry about, and if so are there better options? I'm only 30 so I don't know if melatonin would be a better bet. Ambien is nice as well, but pharms are spendy. Any facts?