Study Reveals how Child Abuse can lead to Substance Abuse
FOR IMMEDIATE RELEASE:
January 04, 2002
Belmont, MA - A five-year study by McLean Hospital researchers has provided a significantly new understanding of how childhood physical or sexual abuse increases the risk for substance abuse in adulthood. While researchers have long known that child abuse increases the risk for substance abuse in adults, a clear developmental mechanism by which this phenomena occurs has remained obscure until now.
In the January 2002 edition of Psychoneuroendocrinology, Carl Anderson, PhD, research associate in McLean's Developmental Biopsychiatry Research Laboratory and Brain Imaging Center, and his colleagues found that repeated sexual abuse affects the blood flow and function of a key brain region related to substance abuse, the cerebellar vermis. This part of the brain has been recently implicated in the coordination of emotional behavior, is strongly affected by alcohol, cocaine, and other drugs of abuse, and may help regulate dopamine, a neurotransmitter critically involved in addiction.
Anderson and colleagues examined the cerebellar vermis because it develops slowly and is exquisitely sensitive to stress hormones. This brain area is stimulated by rocking movements, and earlier work in primates shows that this region plays an important role in infant development.
"Damage to this area of the brain may cause an individual to be particularly irritable, and to seek external means, such as drugs or alcohol, to quell this irritability," said Anderson.
Interestingly, the cerebellum, the region of the brain in which the cerebellar vermis is located, has become a renewed focus of psychiatric research.
Using functional magnetic resonance imaging (fMRI), Anderson and his colleagues analyzed resting brain blood flow in the cerebellar vermis of 32 subjects, ages 18 to 22.
Fifteen of the subjects had a history of childhood abuse; the other 17 were control subjects. A rating scale called the limbic system checklist-33 (LSCL-33), developed at McLean Hospital, was used to assess the degree of irritability in the limbic system, a collection of brain regions known to be involved in the regulation of emotions and memory. Previous research at McLean has shown that childhood abuse is associated with elevated LSCL-33 scores.
A direct connection between LSCL-33 ratings and measures of blood flow in the cerebellar vermis was found. Higher LSCL-33 scores were associated with greater blood flow in both abused subjects and controls; however, the controls had higher overall blood flow measures. This suggests that abuse impaired the development of the vermis and left the subjects less able to regulate and control irritability within their limbic system.
Further, Anderson and colleagues found in a sample of 537 young adults that college students who frequently abused drugs had much higher LSCL-33 scores than college students who did not abuse drugs. Drug abusing college students also had higher levels of depression and anger-irritability, though an elevated LSCL-33 score was most strongly associated with substance abuse.
Combining data from the two studies, Anderson and colleagues suggested that childhood abuse impairs the development of the cerebellar vermis, one function of which is to control and limit irritability in the limbic system. These individuals are then more likely to use drugs to compensate for this deficiency.
Anderson said the team's findings enhance understanding of the developmental mechanisms of childhood sexual abuse, which may result in new methods of treatment for child-abuse survivors.