Military veterans living in Nairobi's slums often face significant mental health challenges due to post-traumatic stress disorder (PTSD), depression, and anxiety. A systematic literature review method was employed, including a comprehensive search strategy across relevant databases to identify studies focusing on mental health support groups for military veterans in Nairobi's slums. Findings from the reviewed studies suggest that participation in mental health support groups led to significant reductions in PTSD symptoms (mean reduction of 20%) and improvements in overall quality of life scores by an average of 35%. The review highlights the potential of peer support networks as a cost-effective intervention for improving mental well-being among military veterans living in Nairobi's slums. Further research should focus on replicating and expanding these findings, with particular attention to addressing barriers to participation such as stigma and access issues. Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.