Johannesurt har ifølge systematiske reviews dokumentert effekt mot klinisk depresjon. Også de alvorlige. Det har jeg sett før, og akseptert at de fremste problemene ligger i at som urtemedisin har man ofte en usikker dose, og at det er en del effekter på annen medisinering man må være på vakt mot.
Derimot var jeg faktisk ikke klar over at det er en ukjent usikkert og noen litt spesielle spørsmål man bør stille til de systematiske gjennomgangene.
Det ligger riktignok et tydelig hint i Cochrane reviewet, som kan fortelle at «Both in placebo-controlled trials and in comparisons with standard antidepressants, trials from German-speaking countries reported findings more favourable to hypericum.»
Det blir ellers rapportert «significant heterogeneity in trials» og at blant det som var «significantly associated with effect sizes» finner vi også «country of origin (p = 0.002)».
Mer spesifikt, kunne Neuroskeptic fortelle var det slik at
The analysis concluded that overall, St John’s Wort was significantly more effective than placebo. The magnitude of the benefit was similar to that seen with conventional antidepressants in other trials (around 3 HAMD points). However, this was only true when studies from German-speaking countries were examined.
Out of the 11 Germanic trials, 8 found that St John’s Wort was significantly better than placebo and the other 3 were all very close. None of the 8 non-Germanic trials found it to be effective and only one was close.
Det er nokså oppsiktsvekkende. Spørsmålet er hva det betyr. Det betyr ikke nødvendigvis at det er snakk om publiseringsbias, slik man med svært gode grunner mistenker den overveldende graden av positive funn i kinesisk akupunkturforskning (ca. 100%). Det kan også være andre årsaker, slik Stuff and Nonsense tar for seg:
St John’s Wort may actually work better in German trials because German investigators tend to recruit the kind of patients who respond well to St John’s Wort.
Perhaps the credibility of a therapy in a particular country actually influences trial results. If this is the case, then I should probably expect to see more positive results for acupuncture in China than in England, more positive trials of St John’s wort published in Germany than in England – and perhaps even a tendency for US studies of chiropractic to be more positive than those conducted in England.
Vi vet ikke, ser det ut til.
Men en ting det ikke later til å bety, er at konvensjonelle antidepressive midler er veldig mye bedre. For den tyske positiviteten er synlig mest i sammenligning mot placebo, kommenterer Neuroskeptic:
The picture was a bit more clear when St John’s Wort was directly compared to conventional antidepressants: it was almost exactly as effective. It was only significantly worse in one small study. This was true in both Germanic and non-Germanic studies, and was true when either older tricyclics or newer SSRIs were considered.
Interessant, ikke sant?
(Via Stuff and Nonsense, som tar opp flere interessante ting. Nå tilbake til vodou.)