INTRODUCTION We should not assume that we know a lot about either depression or addiction. These illnesses are causing terrible morbidity and mortality despite the availability of treatments. This chapter reviews substantial evidence that both illnesses are due to a lack of relatedness. We need to learn more about why persons suffer from lack of relatedness, and what treaters can do about it. Psychotherapy may be the best treatment available. We prescribe medications to some patients with depression and addiction. While medications appear to improve outcomes, the mechanism of action is unclear. Prescribing for patients with depression and addiction varies substantially from that with nonaddicted patients, because of the danger of potentially abused mediations, and because of alterations in brain function caused by addictive drugs and addictive drinking of alcohol-especially damage to neural systems that initiate and preserve sleep.

The Prevalence and Comorbidity of Depression and Addiction To discuss the comorbidity of depression and addiction, we must be able to define each. Already we are in a difficult position. Exactly what depression is, and exactly what addiction is, may not be definable with our current level of knowledge. For example, if depression is such a devastating illness, why then is it so prevalent? Why would not the genetic line of individuals with a predisposition to depression have died out millennia ago? How could depressed people survive prehistorical conditions? We must conclude that depression must have some functional use. And what exactly is addiction? Perhaps we could all agree that injecting heroin daily is addiction. But where do we draw the line on drinking? Is it daily drinking? Is gambling an addiction when there are serious consequences? What could the brain mechanism be? Could one be addicted to surfing the Internet, to exercise, or to watching television?