3.3 The Interdependence of Nature and Nurture

Interdependence of Nature and Nurture

• The concept emphasizes that nature (genetic factors) and nurture (environmental factors) are interdependent.

• Misconceptions in media:

  • News headlines often simplify complex relationships, e.g., "Scientists found gene for autism".

  • Such statements oversimplify the nature of genetic influence on behavior.

Complexity of Genetic Influence

• Simplified Explanations:

  • The phrase “found the gene for” suggests a direct link between a single gene and a behavioral trait.

  • Most genes influence multiple traits and behaviors, not just one specific outcome.

Genes and Proteins

• Fundamental Role of Genes:

  • Genes code for proteins, not directly for behavioral traits or conditions.

  • Proteins combine and perform various functions, thereby participating in multiple biological processes.

  • Key Point: There is no singular gene responsible for complex psychological traits.

Genetic Inheritance and Risk

• Inheritance vs Guarantee:

  • Inheriting a genetic marker does not ensure a corresponding characteristic or disorder.

  • Example disorders like Alzheimer’s and Parkinson’s are not solely determined by genetic vulnerability but involve a combination of genetics and environmental factors.

Case Study: Genetics of Depression and Anxiety

• Graphical Representation:

  • Y-axis: Probability of developing depression

  • X-axis: Number of stressful life events

  • Each line represents different genetic variations of a specific gene involved in neurotransmitter regulation linked to depression.

Versions of the Gene

• Two versions of the gene in question:

  • Short version and long version.

  • Genetic combinations:

  • Homozygous short: Two copies of short version.

  • Homozygous long: Two copies of long version.

  • Heterozygous: One short version and one long version.

• Research Findings:

  • Inheriting short version(s) may increase risk of developing depression, but only in combination with environmental factors.

  • Important Insight: Environmental stress enhances the genetic risk.

Interaction of Genetics and Environment

• Observation from the graph:

  • Individuals not exposed to stress show low risk for depression, regardless of genetic makeup.

  • As stress levels increase, the probability of depression diverges based on genetic variants.

  • The homozygous short variant shows a significant increase in risk with higher stress levels.

• Overall Conclusion:

  • Interdependence is critical: Nature and nurture interact dynamically, with 100% involvement of both to influence mental health outcomes.