Biological explantions of schizophrenia - genetics

Family studies

• gottesman large scale family studies showed children with two SZ parents have concordance rate of 46%, one parent 13% and sibling 9%

Twin studies

• Joseph calculated that pooled data for all SZ twin studies prior to 2001 showed a concordance rate of MZ twins of 40% and 7% for DZ

+ all twins studies show higher concordance in MZs - more reliable argument. But concordances are not 100%

- although recent ‘blind; studies have found lower concordances. They also use very small samples. There are very few MZ twins in the population and only 1% are SZ

Adoption studies

• tienari er al large scale study in Finland found high rates of diagnosis in adoptees who biological parents were SZ (6.7%) compares to control adoptees born to non-SZ mothers (2%)

Candidate gene research

• benzel et al identified three genes that have all been associated with high dopamine levels which lead to positive symptoms

• Ripke et al carried out a huge study combining all the data from previous genome studies comparing the genetic makeup of 37000 schizophrenics and found 108 separate genetic variations were associated with the risk of schizophrenia . SZ is therefore likely to be polygenic

What can we conclude from this?

+strong evidence that genetics are a risk factor. But concordances not 100% - search for relevant genes - can’t yet find a specific gene

-can’t help to cure until we understand the specific genes involved. SZ involves huge number of genes each making only a small contribution