Addiction – impulsive or compulsive?

In a recent reply to a reader’s comment, I waxed eloquent about whether addiction was an impulsive drive or a compulsive drive. Let’s consider the matter more closely. According to neuroscientist Trevor Robbins, impulses can be defined as urges or acts that arise from an input that you can’t inhibit. In other words, the problem is in the input stream—thoughts, perceptions, and stimuli that are just too attractive to turn off. Compulsion, says Robbins, is an urge to act that is too powerful to turn off, so you keep doing the thing again and again. Now the problem is in the output stream, and the classic case is OCD—obsessive-compulsive disorder.

Present scientific wisdom on addiction would classify it as an impulsive disorder. Because, according to neuroscientist Kent Berridge, addictive cravings are always cue-related. You don’t just crave. First, there has to be a stimulus, a cue, to make you think about the thing you want. That cue can be of any sort. It can be the runny nose of opiate withdrawal, the name of a dope connection suddenly showing up on the screen of your mind. It can be just the sight of last week’s leftovers – a few paltry grains of powder, a leftover pill, whatever. Then, suddenly, wham! you want it now. The ventral striatum, the seat of craving, is highly sensitized to drug cues through repeated exposure: based on a buildup of synaptic networks that provide a potent meaning for the drug, plus the surge of dopamine directly triggered by previous associations.

But compulsion can play a huge role in addiction as well. We feel “compelled” (not “impelled”) when we reach for the drug (or the drink or food or link to our favourite gambling site) again and again and again. Even after you’ve taken a dose of whatever it is in the last half hour, you just feel that it’s not enough, and the urge is to take more, no matter what the consequences. The consequences can be pretty severe. Coke and its cousin crack are the best examples. A coke high can last for an hour or two, but cokeheads snort more and more, sometimes minutes apart, just in case there’s not enough already inside them, and that can lead to a stroke or heart attack. With opiates, compulsive consumption can obviously lead to an OD. The source of compulsion is some kind of deep anxiety, but more on that another time.

The striatum has a component that focuses attention on the goal. That’s the ventral striatum, and it’s a key player in drug craving. But the striatum also has a motor component that generates action. The “dorsal striatum” releases actions, something like bullets from a gun. It puts the actions into effect. And there you are doing it – again! – before you’ve even thought about it. The dorsal striatum is the culprit when it comes to compulsive (repetitive) behaviour. But the close linkage between these two parts of the striatum – attention to the goal (ventral) and execution of the goal (dorsal) – is what moves us from impulse to compulsion.

That’s not good news for addicts of many stripes. But what can I say? Be careful! We have to live with the hardware in our heads, so we’d better get to know it and learn how to use it properly.