Eating disorders and drug abuse

Drug addiction is a multifactorial disorder that results from the interaction between genetic and environmental factors. Addictive behavior is characterized by a compulsion to seek and use the drug, a loss of control over intake, and the emergence of a negative emotional state when access to the substance is prevented. Substance use disorder (TUS) must be considered a chronic disease, since even after a satisfactory detoxification process and long periods of abstinence, it is common for the addict to relapse into consumption. Numerous factors that can influence the development of addiction have been studied, such as genetics, the influence of friends during adolescence, exposure to stressful situations, lack of social support, etc. However, there had been virtually no studies evaluating the role of diet in vulnerability to developing an addictive disorder. For the last few years, a series of studies have been carried out on animal models in which it has been demonstrated that the consumption of a diet high in sugar or fat favours the consumption of certain drugs.

Our research group has shown that mice that ingest a high fat diet intermittently (binge model) have a much higher consumption of cocaine and ingest more alcohol than those that are fed a balanced diet. These fatty binge foods are reminiscent of the typical compulsive behaviors that are a fundamental feature of the addictive process. But why do animals (and also humans) love food rich in fat or sugar?

Eating is an essential necessity for survival and is one of the great pleasures of the human being. From an evolutionary point of view, our organism developed in a context characterized by nutritional scarcity and obtaining food was a fundamental objective for survival. Since our body processes food quickly, we present an innate preference for foods with high energy content and very high calories, because in a situation of scarcity would be an energy reserve that would help us to survive. These foods, like drugs of abuse such as cocaine, alcohol or nicotine, cause a release of dopamine in the brain reward system, which explains the feeling of pleasure we experience when consuming them. In today’s society, there is such an abundance and variety of foods that this evolutionary adaptation aimed at feeding for survival becomes a danger, since we eat not only for hunger, but also for pleasure. In recent decades there has been a dramatic increase in the incidence of obesity in developed countries, Spain being a country especially affected. Obesity affects not only the adult population, but also children, especially adolescents.

Although they are still scarce, some studies carried out in our country have shown that patients with eating disorders (ED) consume, mostly three addictive substances: caffeine, alcohol and tobacco. This psychiatric comorbidity complicates the evaluation of both disorders and their subsequent treatment. However, virtually no studies have been conducted in drug-addicted populations to assess whether eating disorders occur more frequently than in the general population. For this reason, we carried out a study in an Addictive Behaviour Unit in the Valencian Community which showed a greater presence of ACT in the population studied. The participants who presented TUS obtained higher scores in all the scales that pointed to the presence of an ACT, being especially high the scores observed in the addicted women. Most of the patients presented addiction to alcohol, cocaine or were polyconsumers, and high scores were observed in all of them referring to impulsivity. Among the ACTs, alterations in appetite and satiety, obsessive and compulsive behaviours and self-destructive behaviours were observed. These results are comparable to previous studies on this comorbidity in other countries.

These studies warn especially about the risk in the adolescent population, where excessive fast food intake behaviors often occur along with large amounts of alcohol. There are a large number of factors that explain this comorbidity, such as loss of control, sensitivity to reward (whether through drugs or food), low self-esteem or self-medication, using drugs or food to alleviate a negative emotional state. But a gateway theory has also been put forward between food consumption and substance abuse, which postulates that compulsive food intake may facilitate the development of another unadaptive behaviour, such as drug use. During a period when the brain is especially plastic, the ingestion of highly reinforcing food can modify the brain’s reward system of these young people and change the way in which they respond to drugs, increasing their vulnerability to addiction.

These studies indicate that TCA control or screening should be included in the addicted population, as both disorders can alter the course of the disease and the development of treatment. Intervention and prevention should be focused from adolescence, the critical age for the onset of these disorders.

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