Unfortunately, without access to the full article, I can't say for sure what the authors argue, but another possible explanation for the long delay between treatment onset and the reduction of depression is that SSRIs act as an active placebo.<p>If so, SSRIs are "active" because they do change <i>something</i> in the brain (unlike a corn starch placebo), but a placebo because the thing changing (serotonin levels) is unrelated to depression. However, since we know something is changing, we believe we'll get better... and thus, we do.<p>(Think of an active placebo like menthol in dandruff shampoo. Menthol makes the scalp tingle and convinces us it's working, but does nothing for the scalp itself.)<p>Regardless, there's a lot of gaps and unexplained weirdness in how antidepressants work, so there's still a lot of work to be done.