Key takeaways

  • The three categories internalizing, externalizing, and thought disorder was an attempt to sort diagnoses into three overarching categories. Some problems:

  • Correlations were very high even across these domains

  • Longitudinal data showed that one diagnosis at time 1 predicted the same disorder, but also other disorders at later time points

  • Heritability of psychiatric disorders is strong, but with very little specificity

  • Importantly, we don’t know about the causal directions here.