Wednesday, 30 May 2012
In one of the first papers published on "therapy genetics", Kathryn Lester and her colleagues, including Thalia Eley, took swabs from hundreds of white children with anxiety, aged 6 to 13. The researchers were specifically interested in the genes the children had that code for Nerve Growth Factor (NGF) and Brain Derived-Neurotrophic Factor (BDNF) - proteins involved in the survival and development of neurons. The children, some based in the UK and some in Australia, then underwent a CBT programme designed for helping anxious children. The key question was whether the children's genetic profile would be associated with how well they responded to the treatment.
There were no genetic associations with the children's immediate response to the treatment. However, at follow up (assessed at 3, 6 or 12 months), the children's particular NGF genotype was related to their therapeutic responsiveness. We each have two copies of the NGF gene, rs6330, which can come in two versions, known as the T allele or the C allele. Lester and her team found that among children with two copies of the T allele version, 76.7 per cent were free of their primary anxiety diagnosis at follow up, compared with 63.5 per cent of children with one C version and one T version, and just 53.2 per cent of children with two copies of the C allele. These associations held, even after controlling for other clinically relevant factors such as age, gender and geographical location.
Why should the children's particular form of NGF gene affect the way they respond to CBT? Definite answers will only come from more research, but Lester and her colleagues argued that the finding makes sense based on what we already know about NGF being involved in the growth of new neurons and in changing connections between existing neurones - known as "neuroplastic changes" in the scientific jargon. "Significant learning experiences of the kind undertaken during CBT may very well be underpinned by neuroplastic modifications in brain activity and function," they said.
This new result complements another recent paper published by the same research group, in which anxious children responded more successfully to CBT if they had a particular version of a gene involved in the activity of the neurotransmitter serotonin. Again, the association was found at follow-up rather than immediately after therapy.
Lester and her team said they believed the association they documented in this new research is "clinically meaningful", but that "clinically significant prediction by genetic markers is likely to be best achieved by combining multiple genetic markers (perhaps in combination with clinical predictors) into predictive indices or algorithms."
The research has some shortcomings. For example, without a no-treatment control group of anxious children, it's not possible to say for sure that NGF genotype is specifically associated with therapeutic responsiveness rather than an advantageous tendency to recover regardless of treatment. "These findings should be considered preliminary," the researchers said.
Lester, K., Hudson, J., Tropeano, M., Creswell, C., Collier, D., Farmer, A., Lyneham, H., Rapee, R., and Eley, T. (2012). Neurotrophic gene polymorphisms and response to psychological therapy. Translational Psychiatry, 2 (5) DOI: 10.1038/tp.2012.33
Post written by Christian Jarrett for the BPS Research Digest.