In a recent study, researchers developed a new procedure to understand how the tendency to use alcohol as a coping mechanism increases the vulnerability to compulsive drinking. Using rats as subjects, the researchers identified individual differences in coping strategies and how these relate to compulsive alcohol consumption. The research has been published in Brain Communications.
Alcohol use disorder is a significant public health issue, exacerbated by the COVID-19 pandemic, which has seen increased rates of problem drinking. Previous preclinical models of alcohol use disorder have not adequately addressed the role of individual tendencies to use alcohol as self-medication. The new study aimed to fill this gap by creating a model that mimics the human experience of drinking to cope with stress.
“I have been working in the individual vulnerability to develop substance use disorder for over 20 years. The fact that not all individuals who engage in recreational drug use develop an addiction remains something that the general public may not grasp, but it has long been established,” said study author David Belin, a professor at the University of Cambridge and the head of the Cambridge Laboratory for Research on Impulsive and Compulsive Disorders (CliC).
“The psychological and neural basis of such vulnerability have not been elucidated yet. However, epidemiological research has long suggested that the reasons why someone takes drugs (self-medication for instance); hence the psychoaffective state of the individual at the time they use, rather than the primary effects of the drugs, may be determinant contributors to the transition from recreational drug use to addiction. This is the hypothesis we set out parametrically to test in this longitudinal study.”
The researchers used a procedure called schedule-induced polydipsia (SIP) to study excessive drinking behavior in rats. SIP involves exposing rats to intermittent food delivery while they have free access to water or alcohol. This setup creates a situation where some rats develop excessive drinking behavior as a way to cope with the stress of intermittent food availability.
In the first stage, the rats were subjected to 20 sessions where they had free access to water while food pellets were intermittently delivered. The researchers measured the water consumption of each rat to identify those that developed excessive drinking behaviors (High Drinkers, HD) and those that did not (Low Drinkers, LD).
The second stage involved replacing the water with a 10% alcohol solution and repeating the 20 sessions. This SIP alcohol training allowed the researchers to observe if the rats developed a drinking response with alcohol.
To further understand the rats’ coping mechanisms, the researchers categorized the rats based on their drinking behaviors. They identified rats that used water as a coping mechanism (water copers) and those that only developed a coping response when alcohol was available (alcohol copers).
One of the key findings was the persistence of drinking behavior despite negative consequences. The alcohol copers continued to drink the alcohol even when it was adulterated with quinine, making it bitter and unpalatable. This persistence mirrors the compulsive alcohol consumption seen in humans with alcohol use disorder.
“That we could identify individual rats that, very much like some humans do, rely on alcohol to cope with stress was incredible,” Belin told PsyPost.
The study also highlighted the role of stress in driving these behaviors. The intermittent food delivery created a stressful environment, leading some rats to develop maladaptive coping strategies, such as excessive drinking. The introduction of alcohol provided an alternative coping mechanism for some rats, leading to a transition from water to alcohol consumption.
Overall, the study provides a valuable model for understanding how the use of alcohol as a coping mechanism can lead to compulsive drinking. The findings suggest that individual differences in coping strategies play a significant role in the development of alcohol use disorder. This model can be used to further investigate the neural and psychological mechanisms underlying these behaviors and to test potential therapeutic interventions.
The findings also highlight that “one should never drink or take any other drugs as a means to alleviate/numb emotional or physical pain or anxiety,” Belin said.
“In the future, we hope to develop a machine learning-based classifier to identify vulnerable individuals more objectively,” he added. “This requires a much larger dataset than the one we have produced so far.”
The study, “Characterization in the rat of the individual tendency to rely on alcohol to cope with distress and the ensuing vulnerability to drink compulsively,” was authored by Lucia Marti-Prats and David Belin.
