The two groups of Caucasian males we recruited from these longitudinal studies were all born in families with a low socioeconomic status and were living within 200 km from our laboratory at the time of recruitment. The first group was recruited from the chronic physical aggression trajectory (chronic physical aggression group, CPA, n = 8). The control group was recruited from the other three developmental trajectories (Control group, CG, n = 25). Quantification of 10 cytokine levels in plasma was done by ELISA for these subjects (sample 1) using the Quantibody® Human Inflammation Array 1 from RayBiotech (Norcross, United States). The ELISA results showed that compared to the control group, the CPA group had significantly lower levels in plasma of five cytokines; lower pro-inflammatory interleukins IL-1α (T(28.7) = 3.48, P = 0.002) and IL-6 (T(26.9) = 3.76, P = 0.001), lower anti-inflammatory interleukin IL-4 (T(27.1) = 4.91, P = 0.00004) and IL-10 (T(29.8) = 2.84, P = 0.008) and lower chemokine IL-8 (T(26) = 3.69, P = 0.001) (see [32] for details). From these subjects (sample 1), the methylation analysis
