A meta-analysis has provided support to the previously suggested idea that a certain gene's variation is linked to suicidal behavior. The gene in question is the one that codes for BDNF (or brain-derived neurotrophic factor), a protein that performs the role of growth factor in nervous system development. After comparing 11 studies and adding data they had gathered themselves (resulting in a total of 3352 people, of whom 1202 had a history of suicidal behavior), the authors were able to confirm that people with the methionine (see figure 1) variation of the gene ran a higher risk of exhibiting suicidal behavior than those with the valine (see figure 1) variation.

Figure 1: The amino acids methionine (left) and valine (right), in skeletal (top) and 3D (bottom) view.

(Source: Wikimedia Commons, users: NEUROtik and Benjah-bmm27)

Luckily, the researchers are very much aware that they have not found ‘the gene for suicide’, but rather remain careful in their assertions. While they do state that the ‘met-variation’ of BDNF might increase the risk of suicidal behavior, the authors are aware of several potential caveats.

First, other genetic factors might be (and almost certainly are) at play here. Single-gene behavioral traits are rare. In the words of the authors:

Additional genetic factors are probably involved in risk for suicidal behaviour. Testing genes along BDNF signalling pathways could shed light on underlying biological epistases.

The environment and epigenetic alterations are also very likely to play a role (basically, behavior is the result of interactions between genes and environment, in different relative proportions for different traits). In the words of the authors:

Environmental stress has been shown to reduce BDNF levels. Epigenetic interrogation of the BDNF gene may provide insight into the effect of the environment on BDNF expression and add to the genetic findings.

Still, given the correlation between suicidal behavior and variation in the BDNF gene, the researchers hypothesize that there might be some route to suicide prevention here:

Given that the low-functioning BDNF Met allele appears to be a risk factor for suicidality, it could be hypothesized that a compound that increases BDNF function may be helpful for suicide prevention.

They do, however, remain cautious in their overall conclusion:

Nonetheless, further replication studies and functional analyses are required to better understand how decreased BDNF signalling may be contributing to suicidal behaviour.

Reference

Zai, C.C.; Manchia, M.; De Luca, V.; Tiwari, A.K.; Chowdhury, N.I.; Zai, G.C.; Tong, R.P.; Yilmaz, Y.; Shaikh, S.A.; Strauss, J. and Kennedy, J.L. (2011). The brain-derived neurotrophic factor gene in suicidal behavior: a meta-analysis. International Journal of Neuropsychopharmacology. doi:10.1017/S1461145711001313.