A recent twin study found limited evidence of a direct causal relationship between moderate cannabis use and most negative psychological outcomes, suggesting that shared genetic and environmental factors largely explain these associations. However, it identified modest yet significant effects of cannabis use on specific areas, including illicit drug use. The findings have been published in the Journal of Psychopathology and Clinical Science. “Cannabis is recreationally legal for adult use in many states now,” said study author Stephanie Zellers, a postdoctoral researcher at the Institute for M…