Increase in pleasurable effects of alcohol over time can predict alcohol use disorder
University of Chicago Medical Center
Moreover, when retested on their
responses 10 years later, those who became alcoholics had the highest levels of
alcohol stimulation, liking and wanting -- and these were heightened compared
to their baseline with no signs of tolerance to these pleasurable effects.
The research, published on Jan. 5 in
the American Journal of Psychiatry, followed a cohort of 190 young
adults in a laboratory-based binge-drinking scenario at three regular intervals
over the course of 10 years.
These results indicate that
individuals developing an AUD are more likely to be sensitized to the effects
of alcohol -- that is, they experience a stronger positive response -- rather
than habituated to the substance with a lower level of response. In these same
individuals, alcohol was less sedating for them from the beginning and this did
not change over time.
"Prior longitudinal studies have looked at young drinkers' response to alcohol and focused primarily on the fatiguing and impairing effects of alcohol," said lead author Andrea King, PhD, professor of psychiatry and behavioral neuroscience at UChicago Medicine. "The thinking that alcoholics do not like the effects of alcohol over time is based on ad-hoc reports of patients entering treatment. Only by testing the same people over a substantial amount of time to see if alcohol responses change over time were we able to observe this elevated response to alcohol compared with placebo, and in participants who did not know the contents of the drinks, so expectancy effects were minimized."
The study showed that higher
sensitivity to the euphoric and rewarding effects of alcohol can predict who
will go on to have an AUD as they progress through their 20s and 30s.
"These pleasurable alcohol
effects grow in intensity over time, and do not dissipate, in people
progressing in excessive drinking," said King. "This tells us that
having a higher sensitivity to the rewarding effects of alcohol in the brain
puts such individuals at higher risk for developing addiction. It all fits a
picture of persistent pleasure-seeking that increases the likelihood of
habitual excessive drinking over time. Alcoholics were thought to need to drink
more to finally get their desired effect when they drink, but these
well-controlled data do not support that contention. They get the desirable
alcohol effect early in the drinking bout and that seems to fuel wanting more
alcohol."
While it may seem relatively
intuitive that individuals who experience alcohol's pleasurable effects most
intensely are at the greatest risk for developing drinking problems, King's
findings run counter to current prominent addiction theories.
"Our results support a theory
called incentive-sensitization," said King. "In response to a
standard intoxicating dose of alcohol in the laboratory, ratings of wanting
more alcohol increased substantially over the decade among the individuals who
developed more severe AUD. Additionally, the hedonic response -- essentially,
how much a person liked the effects -- remained elevated over this interval and
didn't go down at all. This has traditionally been the crux of the lore of
addiction -- that addicts don't like the drug (alcohol) but can't stop using
it."
The participants were regular light
or heavy social drinkers in their mid-20s at the start of the trial from 2004
to 2006. They were brought back for repeated testing of alcohol responses in
the laboratory five and 10 years later as they approached middle adulthood. In
between testing periods, participants were interviewed at near-annual intervals
to track their drinking patterns and symptoms of AUD over time.
King hopes that these results can
help improve our understanding of how some individuals have more vulnerability
to developing AUD, while others remain social drinkers over their lifespan. She
also points out that the results can help to develop better treatments for AUDs
and inform earlier interventions for individuals who may be at high risk for
developing an addiction.
"I'm already using this
information to inform how I talk about addiction with my therapy clients,"
King said. "It can be frustrating for them to see other people who can
have a couple drinks and just stop there. They can't understand why they
repeatedly seem unable to do that, too, and I tell them, it may be because your
brain responds differently to alcohol that makes it harder to stop drinking
once you start. Knowing that information can empower a person to make different
decisions. Even with our current pandemic, a person may drink to cope with
stress or reduce negative feelings, but that doesn't mean that they don't also
experience the buzz, or pleasurable effects from drinking. This is most
concerning for at-risk drinkers as those responses may intensify as they
progress with heavier drinking."
Based on this research, King sees
the potential for a sort of "personalized medicine" approach for
treating AUDs, describing how sharing an individual's "thumbprint"
response to alcohol can make a difference in how they think about their
consumption.
"This could be an opportunity
for early intervention, comparable to how someone may get their cholesterol
tested and then may be more motivated to change their diet, exercise more or
start a medication to rein it in," King said. "Similarly, knowing
one's acute response to alcohol and how it may indicate a person's future risk
for drinking problems, one may decide to change their drinking on their own or
seek help to avoid the progression to addiction."