Genetic and environmental factors of schizophrenia and autism spectrum disorder: insights from twin studies.
Level 5 - mechanism / opinion, no new human data
Narrative review summarizing twin study methodology, epigenetic mechanisms, and environmental factors without systematic review methodology.
PubMed 32285255 · doi:10.1007/s00702-020-02188-w
What was done
This narrative review summarizes classical epidemiological twin study designs (concordance comparisons between monozygotic and dizygotic twins) and modern molecular approaches used to study schizophrenia and autism spectrum disorder. It reviews the application of next-generation sequencing, tissue-specific epigenetic profiling (using peripheral blood, postmortem brain neurons, and induced pluripotent stem cells), and microbiome assessments in disease-discordant monozygotic twins.
What was found
The abstract reports no quantitative results, statistical values, or effect sizes. It highlights qualitative shifts in the field, noting a growing emphasis on epigenetic divergence over primary DNA sequence mutations to explain monozygotic twin discordance, the necessity of testing neural or stem-cell-derived tissues due to tissue-specific epigenetic marks, and the exploration of intestinal flora and transgenerational epigenetic inheritance as explanatory factors.
Why it matters
Examining molecular and epigenetic differences within discordant monozygotic twin pairs provides a unique paradigm to isolate environmental and non-genetic contributors to complex neuropsychiatric disorders.
Limits
The abstract contains no primary data, sample sizes, search methodology, or quantitative synthesis. Many mechanisms discussed (such as gut microbiome influences and transgenerational epigenetic transmission in psychiatric discordance) remain exploratory hypotheses.
Cited by
- supports Identical twins do not always both develop schizophrenia.