The relationship between depression and drug abuse is a particularly troubling one, and it’s often difficult to meaningfully distinguish one disease from the other. Put simply, the relationship between depression and drug abuse is predicated on chemistry, and affect, and the plain fact that human beings will always do what feels good. To the extent that depression imposes an unspeakable sort of pain on its victims, drug use and abuse offer a sort of chemical balm, a mechanism by which the disease might be made to a hurt a little bit less. Indeed, so intertwined are depression and drug addiction that it’s almost uncommon to find one without the other.

First, a word on causality: Does drug addiction cause depression, or does depression cause drug addiction? There is, simply stated, no obvious answer to that question, and the mechanisms of addiction and depression are different for every individual patient. For our purposes, the important issue is not so much the question of which disease causes the other as it is the plain that both diseases very often exist in tandem. Put it this way: There’s no use crying over spilled milk, and there’s not much sense in trying to figure out exactly the stuff got on the floor. What matters is cleaning it up, and ensuring that accidents don’t happen in the future.

But how to do that?: how to make drug rehab and depression treatment work together, and how to best ensure a patient’s long-term health? The answer there lies in the extent to which depression and drug addiction spring from the same source: from the physical and psychological pain that acts as the driving force behind both diseases. Remember, human beings will always do what feels good, and depression hurts like hell. Drug abuse, in that sense, is a logical response, an evolutionary response, even; depression victims abuse drugs because using feels better than not using. There is, in the end, no more incisive truth than that.

And what that truth means, again, is that depression treatment is often only as effective as the drug treatment which accompanies it. As noted above, getting better means getting all the way better, and no depression treatment program which fails to account for the full scope and impact of the disease can hope to help its patients achieve any kind of lasting recovery. Depression doesn’t work part-time, and neither can depression treatment. Health, real health, can only ever be an all-consuming proposition.