Stockholm Psychiatry Lectures 2019-11-04
Professor Tyrka is interested in the intersection of environment and biology, and how adverse experiences can affect the development of children. Early stress has been identified as a mechanism in both psychiatric and other medical conditions (such as metabolic syndrome and cardiovascular disease). It has also been associated with premature death, both due to natural and unnatural causes.
What are the mechanisms responsible for this relationship? One such mechanism is through the hypothalamic pituitary axis (HPA-axis) which activates the stress-response by releasing glucocorticoids, affecting many regulatory systems in the body. Another proposed mechanism is through the telomere/telomerase maintenance system. The telomeres are located at the end of chromosomes, and preserve the stability of replication in new cells. Their length is reduced over time, and older individuals have shorter telomeres than younger individuals. Telomere shortening is associated with a variety of negative health consequences, and recent research has found that psychosocial stress is associated with shorter telomeres. In Dr Tyrka’s own work, the findings point to an association between childhood maltreatment and shorter telomere length.
Mitochondria are present in virtually every cell, but are particularly common in structures with high energy demand such as the brain and heart. They are involved in energy production, stress response, immune function, and cell signalling. Furthermore, the mitochondrial DNA (mtDNA) also contains genes relevant for the regulation of glucocorticoids. Childhood maltreatment is in this case associated with higher numbers of copy numbers in the mtDNA, suggesting a compensatory mechanism.
In a recent, large scale study of maltreatment in children, Dr Tyrka’s group are studying children at 3-5 years of age. They are therefore able to compare children who have been maltreated within the last 6 months to children with no signs of maltreatment. This can overcome biases related to retrospective studies in adults. The number of traumatic life events and maltreatment were associated with telomere length and mtDNA copy numbers, but it should be noted that the maltreated children had longer telomeres than the control group! Internalising behaviours (depression and anxiety) were also associated with telomere length and mtDNA copy numbers. The same children are now being studied 6 years later, at age 9-11, and data collection is ongoing.
The effects of adverse childhood experiences are not limited to impact on biological systems, but also affect psychosocial and educational functioning. Executive functioning, attachment, self efficacy, attention, memory, and behavioral control are just a few examples where a large body of research has demonstrated detrimental effects. Having an even wider scope, there are also additional societal effects such as homelessness and crime.