I think the question is its own answer. Its a good question.

Dr. Newcombe surely knows this is a very controversial position to take, that flies in the face of the medical "consensus". I happen to disagree - I think substance use disorder results from the combination of three key components: (a) psychosocial risk factors (b) psychological and/or neurophysiological proclivities towards IRRATIONAL RISK-SEEKING behavior (as opposed to RATIONAL RISK-TAKING, like mountain climbing where the climber balances the risk of a negative outcome with the thrill of scaling the rock face) and (c) access to substances of misuse.

Given that the substance use epidemic is killing more people than all other forms of "accidental" death combined, I think it is in a different category from mountain climbing or skiing (although they certainly account for some mortality!). I think this question really calls for a deeper investigation of the epistemology of psychiatry - because one could argue that a skier or mountain-climber who repeatedly injures themselves severely, to the point of destroying their life, but as soon as they recover a bit, begins climbing up another mountain (only to fall off again) has a behavioral addiction, like gambling addiction or sex addiction. I think the standard for something being a disease/disorder is when the morbidity or mortality (e.g. material negative impact on the patient's life) is so great that it substantially offsets their ability to function in other areas of their lives. Philosophically, I have nothing against recreational drug use, with the caveat that it must be voluntary. Patients with substance use disorder, in its more advanced stages, have no choice but to continue ingesting/insufflating/injecting the substance to which they are addicted. I think a mountain climber who couldn't stop climbing a mountain, and couldn't stop falling off the cliff and severely injuring herself, and kept doing it anyway (and did little else in her life) might arguably have a psychological problem or disorder or disease!

I understand your argument, but in my experience many people 'into' risky sports describe their experience in a similar way to habitual drug users: they get huge pleasure (euphoria) from their sport; they crave the thrill of the dangers involved in their sport; they spend all their spare money and time on their risky sport; and they continue doing it for many years despite injuries to themselves or their associates. Yet there is no obvious outcome from their activity except the pleasure they get. For instance, I have a friend who says he is 'hooked' on ice-climbing, spends as much time as he can climbing mountains, gets huge 'rushes' of pleasure from dangerous climbs (including near-falls) - and who has continued climbing despite the death of a climbing friend, and despite losing two fingers while climbing. He says climbing is 'his reason for existence', and would love to end his days during a climb. Very similar to drug use, in many ways.

Point taken, and risky sports may well qualify as a behavioral addiction, but I think something you said undercuts your argument: "they spend all their SPARE money and time" [on the sport].  (1) A substance use disorder patient ends up spending ALL her money and ALL their time using and or pursuing the use of the substance (2) substance use disorder is a progressive illness, e.g. it gets worse until it is often fatal.  I'm not sure that applies to mountain climbing - do they do more and more of it until it kills them?  That's not true of the mountain climbers I know.  I love to ride motorcycles, without a helmet if possible, but I don't do it all the time, and I don't do it to the exclusion of my professional and familial obligations, like a substance use disorder patient does.  I think there are certainly mountain climbers who are "addicted" to the sport, and conversely there are recreational drug users who use drugs for fun (on weekends, etc) and then put them away.  It is hard to define the line where risky behavior crosses into compulsive and obsessive behavior that is often fatal.  

Thanks for the reply, Devin - a great point, with with I agree. It is hard to define the line between dependent and non-dependent drug use and other activities, but your point makes that line clearer (i.e. the distinction between spending all your spare time and spending all/nearly all your time doing something).

This discussion just happened to come up when I logged into RG. We actually discussed behavioral addictions vs. substance addictions at our last Medical Advisory Board Meeting and the neuroscientists in the group held the position, with which I now agree, that they are the same thing, except that the former upregulates endogenous neurotransmitters and the latter upregulates exogenous neurotransmitters (or their pro-drugs, if you will). Mountain climbing probably spikes adrenaline, dopamine, etc etc just as cocaine does. But with most addictions, it is hard to find cases where it is progressive and then fatal. That is, you don't hear many avid climbers saying "First I just climbed on the weekend, then it was every day, then it was at night, until I lost my job and my family and my money and just kept on climbing". However, you do hear similar stories from addicted gamblers. So maybe the line is blurrier than I thought. A better "line" to draw between risky behavior and "addictive" behavior, therefore, might be the concept that the patient feels compelled to continue the behavior *despite* receiving little positive benefit. For example, most advanced SUD pts will state they no longer get "high" from exogenous substances - they rather *need* the substances to prevent themselves from getting physically and psychologically ill. But the same could be said of *some* mountain climbers (maybe), but definitely of patients addicted to sex or gambling or whatever behavior is upregulating neurotransmitters on which they have become dependent for a sense of well-being. Apologies for adding confusion to a topic on which it seemed there was progress, but I think it is important not to label everything copious behavior an "addiction" as the popular press likes to. This diminishes the focus on "real" addictions, especially substance addictions that presently represent a huge epidemic and massive public health crisis. [That said, it's hard to draw the line. I thought the idea of all addictions existing on a neurophysiological substrate, whether to behaviors that upregulate neurotransmitters or exogenous substances that do the same, was a pretty unassailable position -- and unfortunately, it caused me to rethink mine and pose this quandary. Note that the APA has refused to define "addiction" - the DSM V only addresses "addictive disorders" and if I'm not mistaken the word addiction is not in the DSM or ICD-10.]