The brain’s cannabinoid system protects against addiction following childhood maltreatment

Newswise —

A recent study conducted by Linköping University in Sweden has revealed that individuals who have been exposed to childhood maltreatment but do not develop addiction later in life exhibit higher levels of endogenous cannabinoid substances in their bodies. These substances appear to play a protective role against addiction. Furthermore, the research suggests that the brains of such individuals may process emotion-related social signals more effectively compared to those who develop addiction after experiencing childhood maltreatment.

Previous research has established a strong link between childhood maltreatment and increased vulnerability to drug or alcohol addiction in adulthood. A recent study conducted by researchers at Linköping University has further supported this finding, revealing that individuals who have experienced childhood maltreatment are three times more likely to develop addiction compared to those who have not, even after accounting for confounding factors such as genetics and other familial influences.

Markus Heilig, Professor and Director of the Center for Social and Affective Neuroscience (CSAN) at Linköping University, along with other researchers, emphasizes that addiction is not solely driven by a search for pleasure or euphoria, but rather by the drugs' ability to alleviate negative emotions such as stress, anxiety, and low mood. It is believed that childhood maltreatment can alter the function of the brain's distress systems, leading to an increased risk of addiction in adulthood. This theory suggests that the impact of childhood experiences on the brain may contribute to the development of addictive behaviors later in life. Heilig is also a consultant at the Psychiatric Clinic of the University Hospital in Linköping.

The endocannabinoid system, which comprises the body's own cannabis-like substances, known as endocannabinoids, is believed to play a significant role in the context of addiction and childhood maltreatment. This system is known to regulate reactions to stress and discomfort, and emerging research suggests that it may serve as a stress buffer. The endocannabinoid system is involved in various physiological processes and has been implicated in modulating mood, anxiety, and stress responses. Understanding the role of endocannabinoids in mitigating the effects of stress and discomfort could potentially shed light on their involvement in addiction risk and resilience, particularly in individuals who have experienced childhood maltreatment. Further research in this area may provide insights into the complex interplay between the endocannabinoid system, stress, and addiction.

The study, which was published in Molecular Psychiatry, aimed to investigate the mechanisms underlying susceptibility or resilience to developing substance use disorder in individuals who have experienced childhood maltreatment. One challenge in conducting such research is the potential for overreporting of negative life experiences when recalling past events. To address this, the researchers utilized psychiatric care registers to identify participants who had objectively and prospectively documented exposure to childhood maltreatment. The study included approximately 100 young adults who were divided into four equal-sized groups: those who had been exposed to childhood maltreatment and had developed an addiction, those who had been exposed but had not developed an addiction, those who had not been exposed but had developed an addiction, and those who had neither been exposed nor developed an addiction.

The researchers measured endocannabinoid levels in the participants' blood and conducted several experiments to assess their stress reactions. Additionally, magnetic resonance imaging (MRI) was used to scan the participants' brains while their reactions to social stimuli were tested. This multi-faceted approach allowed the researchers to gather comprehensive data on endocannabinoid levels, stress responses, and brain activity in relation to childhood maltreatment and addiction outcomes. The use of objective and prospective measures of childhood maltreatment, along with advanced imaging techniques, adds rigor to the study's findings and provides valuable insights into the potential role of endocannabinoids in addiction risk and resilience.

Interestingly, the group that had experienced childhood maltreatment but did not develop an addiction stood out from the other three groups in the study, and the researchers referred to this group as "resilient". In comparison to the other groups, the resilient group showed increased function of the endocannabinoid system, as well as distinct patterns of brain activity. Surprisingly, the resilient group exhibited the most notable differences compared to the control group, which had not experienced childhood maltreatment nor developed any addictions. These findings suggest that individuals who have been exposed to childhood maltreatment but do not go on to develop addiction may have unique physiological and neurological characteristics that contribute to their resilience. Further research is needed to understand the underlying mechanisms and implications of these findings, but they shed light on the complex relationship between childhood maltreatment, endocannabinoid function, brain activity, and addiction outcomes.

When exposed to emotional social stimuli, the resilient group exhibited higher activity in three specific areas of the brain. Two of these areas are part of a brain network responsible for focusing attention and cognitive abilities on the current situation and modifying behavior accordingly. The third area is located in the frontal lobe, which is associated with emotion regulation. This area of the brain communicates extensively with other areas involved in emotion processing. Humans have a well-developed frontal lobe compared to other animals, which helps regulate impulses and emotions, such as suppressing fear responses in situations where fear is not relevant. These findings suggest that the resilient group may have enhanced cognitive and emotional regulation abilities in response to emotional social stimuli, which could contribute to their ability to cope with childhood maltreatment without developing an addiction later in life. However, further research is needed to fully understand the complex interactions among these brain areas and their role in resilience to addiction.

According to Irene Perini, a staff scientist at CSAN (Center for Social and Affective Neuroscience) at Linköping University, heightened brain activity in specific regions among individuals in the resilient group, who did not develop addiction despite experiencing childhood maltreatment, could be associated with a more adaptive response to emotional social cues. In addition, even during rest, these individuals exhibit increased communication between the frontal lobes and other brain areas, suggesting that they may possess superior emotional regulation skills.

The present study raises a question about whether the resilient group had inherently higher endocannabinoid system function, or if they were more capable of activating the system in response to stress, thereby avoiding the long-term effects of childhood maltreatment. However, due to the cross-sectional nature of the study, it is not possible to determine the answer to this question.

The research, conducted by Markus Heilig's research group at CSAN (Center for Social and Affective Neuroscience), was supported by various funding sources including the Swedish Research Council, Knut and Alice Wallenberg Foundation, Region Östergötland, Linköping University, Systembolaget's Alcohol Research Council, and the Brain & Behaviour Research Foundation NARSAD Young Investigator Grant. The study was co-authored by Irene Perini, who is currently a professor at the University of Calgary in Canada, along with Leah Mayo, who was previously affiliated with CSAN at LiU.