made by scientists that we came across in Chapter 1 – between the Stop and Go impulses in the brain. The Go impulse tells us to reach out for an immediate reward; it’s ancient, it’s powerful and it’s shared with animals. As you might expect, it goes into overdrive at the prospect of food and sex. Dopamine and ‘wanting’ are central to this urge – but different levels of ‘liking’ also determine the strength of the Go message.4
The Stop impulse is highly developed only in humans. It helps us manage our Go impulse by spelling out the consequences of immediate reward. You could call it the voice of reason; it comes from the frontal lobes of the human brain. These are not fully developed in adolescents, who are therefore poor at managing the Stop impulse. This will not come as a surprise to the parents of teenage children.
Let’s return to the traumatic experience of those Parkinson’s patients. Their disease drains the brain of dopamine. Indeed, it may begin to do so decades before more obvious symptoms become apparent. That could explain why Parkinson’s seems to disproportionately affect people with introverted personalities: those self-effacing traits may not be signs of natural, life-long introversion but, rather, the first symptoms of the disease, appearing years before diagnosis.
The patients who developed sudden gambling or other impulsive habits had been given dopamine agonists, which, by boosting dopamine, usually slow down the progression of the disease. They are a common treatment and can be remarkably effective. An aunt of mine with Parkinson’s was given one of these drugs. The brightening of her personality and her fresh pleasure in everyday experiences, such as looking at her garden, seemed almost miraculous. For some patients, however, the same chemical that restored my aunt’s joie de vivre was psychological poison.
Alan Burrows, a pensioner from Queensland, was one of 100 Australians who sued the drug company Pfizer after taking its dopamine agonist medication Cabaser. He claims that it caused him to start binge gambling on ‘pokies’ (Australian slang for slot machines). Eventually, he had to sell his house to pay off his $300,000 gambling debts. ‘Once I started I had to keep going, by withdrawing money every hour, until I couldn’t get any more money,’ he said. ‘It was a compulsion to do it. You became really devious, disgusting.’5
It’s probably no consolation to Mr Burrows, but what happened to him and to the other Parkinson’s sufferers who developed compulsive habits helps us to draw the boundaries of addiction. Their ordeal suggests that dopamine is a common factor in habits that society has been slow to label ‘addictions’ because they don’t involve drugs.
After the stories of bad reactions to Parkinson’s drugs surfaced, Dr Valerie Voon of the US National Institutes of Health led a study of patients given dopamine agonists. She found that 13 per cent exhibited ‘a constellation of pathological behaviours, including gambling, shopping, binge eating and hypersexuality’.6 They did so because they were being over-supplied with dopamine.
The inference we can draw from this is valuable. It seems that people who don’t have Parkinson’s disease but engage in the same pathological habits are also having problems with their dopamine levels. Gambling, obsessive shopping, binge eating, hypersexuality – note how those Parkinson’s patients found themselves caught up in the sort of activities where wanting overwhelms liking. Also, they were being driven by repetitive urges. This is typical of dopamine at work, laying down new patterns in the brain as it takes effect. As the psychiatrist Norman Doidge explains: ‘The same surge of dopamine that thrills us also consolidates the neuronal connections responsible for the behaviours that led us to accomplish our goal.’7
In other words, the more we experience dopamine-induced pleasure, the more we want to repeat the experience. But, thanks to levels of tolerance that have been raised by rewiring, the harder we have to work to repeat it to our satisfaction. That is why addicts always seem to be looking for a bigger and bigger hit.
All substance abusers experience surges of dopamine, often accompanied by craving – that is, very strong feelings of wanting. Alcohol, amphetamine, cocaine, heroin, marijuana and nicotine all increase the supply of dopamine to the nucleus accumbens, a pleasure centre buried deep in the brain that has been called the final destination of the reward pathway.8
This does not mean that addicts are people born with naturally high or low levels of dopamine, nor that they have inherited cravings that force them to keep stimulating the rush of dopamine into their nucleus accumbens. If any of these things could be proved, then the study of addiction science wouldn’t involve so much infuriating guesswork.
Different recreational drugs do different things to the brain. They produce different rewards – and different punishments. You don’t have to take them to know that; you just have to observe the behaviour of their users. It’s a bit like visiting the zoo.
Coke-heads and speed freaks gabble excitedly as they are swept along on a tide of dopamine. When that tide pulls out, they experience a particular sort of come-down. ‘Coke is the drug we save for the time after we get back from clubbing,’ says Olly, 27, a graphic designer. ‘It runs out pretty quickly. Presuming we don’t order more, by 4 a.m. everyone is getting jittery and anxious. You see people’s eyes flicking around the room wondering if anyone’s got any left. A group of four chatty and gobby friends suddenly becomes four individuals chewing the insides of their cheeks. The next morning we go for brunch to cure our hangovers but everyone’s coming down off the coke, snapping at each other. Some people feel blue for days.’
Heroin users don’t inflict logorrhea on their friends: their drug is forcing the brain to over-produce endorphins, those natural euphoria-inducing and painkilling neurotransmitters. Heroin suppresses neurotransmission in the central nervous system, which can produce an exquisitely calm feeling, particularly if your nerves were shot to pieces in the first place. This can take people to the gates of paradise, but also to hell: the come-down is long and usually profoundly depressing, because the nucleus accumbens is extremely sensitive to opioid withdrawal.9
Also, the brain’s self-regulatory process means that junkies quickly need to increase their doses to slow down neurotransmission; in severe cases, they inject themselves hourly in order to maintain a state of mental paralysis. William Burroughs, writing about his last year of addiction in North Africa, said he could look at the end of his shoe for eight hours. And if a friend had visited him and died on the spot, ‘I would have sat there looking at my shoe waiting to go through his pockets’.10
Ecstasy releases serotonin, a neurotransmitter associated with happiness; hence its users’ indiscriminate declarations of affection. ‘One of the reasons I don’t do pills is seeing how fucking annoying people are when they’re “loved up”,’ says Ollie. ‘MDMA [a purer form of Ecstasy] is even worse. You see groups of heterosexual men hugging and kissing each other. There’s this idiotic bear hugging that goes on for hours, and I’m afraid it makes me laugh when I see them at work on Monday, looking sheepish and sad.’ The sheepishness is self-explanatory; the sadness is pure dopamine deprivation.
Alcohol, meanwhile, has been called the most ruthless of all brain-hijackers. Looking back on my drinking, I now have some idea of what was happening to my body; I just wish I’d known at the time, if only to avoid some hangovers of apocalyptic proportions.
Alcohol molecules are quite unlike those of other addicting drugs. They have the ability to speed up the transmission of chemicals that excite us and also, later, those that relax us, sometimes to the point of stupor. We’re talking about a fiendishly complicated neurochemical dance that releases inhibitions and twists moods over
