Internet addicts, gambling addicts and sex
addicts. Chocaholics and
shopaholics. Our everyday speech
promotes the idea that one can become addicted to any pleasurable activity. Certainly, there’s a thread of truth—
these are all compulsive behaviors that can impact people’s lives to varying
degrees. But how similar are they
at a biological level? Is video
game addiction or gambling addiction or food addiction really like drug
addiction in terms of life impact or brain function or are these terms just an example of metaphoric language?
Both gambling
and video game addictions meet many of the formal behavioral definitions of
addiction developed by psychologists, and there are certainly cases where
peoples lives have been destroyed by such compulsive activities. However, these atypical addictions don’t usually have the same
life-trajectory as addiction to drugs.
In fact, recent community-based studies (as opposed to studies of people
in treatment, which are not a representative sample) show that about a third of
gambling addicts and video game addicts are able to break their addictions
within a given year without seeking outside help.
At the
biological level there is now reason to believe that a broad definition of
addiction, encompassing drugs, sex, food, gambling, video games and some other
compulsions is valid. The
developing story is that the medial forebrain pleasure circuit is as the heart
of all of these addictions. The terms “video game addiction” “food
addiction” and “gambling addiction” are not merely metaphors, but rather point
to shared neural underpinnings.
Brain imaging studies have revealed that both gambling and video game
playing engage the medial forebrain pleasure circuit and cause dopamine release
in ventral tegmental area (VTA) target regions. Patients
who are given dopamine receptor agonist drugs (to treat Parkinson’s disease)
have an unusually high incidence of compulsive gambling and their strong urge
to gamble abates when the drug is withdrawn. We’ve already discussed how carriers of the TaqIA A1 allele,
who have reduced dopamine signaling in VTA targets, are more likely to be
struggle with several different addictions: food, drugs, alcohol and perhaps
others as well. This confirms what
we already know anecdotally: anyone who has spent even a little time in a
casino has seen that nicotine addiction, alcoholism and gambling are often
combined, likely reflecting a common underlying disorder of the pleasure
circuit.
In our zeal to
fashion a general theory of pleasure, reward and addiction, we must be careful
not to over-generalize. After all,
we all eat food and have sex, yet most of us don’t become food or sex
addicts. Similarly, most people
can gamble occasionally or play video games or shop or exercise without these
behaviors becoming compulsive and having a negative impact on quality of
life. Even with drugs, most people
who use alcohol or barbiturates do not develop addictions to these substances.
Is the
difference between weakly addictive behaviors like eating and computer-gaming
and highly addictive behaviors like drug-taking fundamentally a quantitative
difference in the strength of pleasure produced? Or, is there some difference in the quality of that
pleasure? These are fundamental
questions that have yet to be resolved.
That said, there is some reason to believe that the exact time-course of
pleasure evoked by a certain behavior has something to do with its potential
for addiction. For example,
cocaine may be injected, smoked, snorted or ingested. It’s well established that smoked or injected cocaine is more
addictive than snorted cocaine.
This is the basis of the crack cocaine epidemic that devastated many
communities in the 1980’s and which continues to be a scourge to this day. The reason that smoked or injected
cocaine is more addictive is because it reaches the brain with a rapid onset
and at high concentration. Snorted
cocaine produces a pleasure rush that comes on somewhat more slowly. Ingested cocaine has an even slower
time-course of onset and is the least addictive route of administration. The same general idea also holds true
for other addictive drugs like amphetamines and heroin: routes of
administration that produce a fast onset of pleasure are most addictive.
However,
there’s reason to believe that the particular time-course of pleasure may be
important for other addictions too.
High-fat, energy-dense meals produce a sharper dopamine surge in VTA
target regions than low-fat, low-calorie foods. Like the difference between snorted and smoked cocaine, this
may reflect the different concentration profiles of glucose in the brain. Evolutionarily, we humans have
come to prefer these foods, an adaptation that served us well in
hunter-gatherer societies but which has helped to promote an epidemic of
obesity in many affluent cultures where fatty, caloric fast food is readily
available.
As usual, Joey Sayers, cuts to the chase.