Stoppage rules and genetic studies of autism.

Joyce et al. (1988) re-checked 46 families with more than one child with autism. They looked at how parents decide to stop having kids after a diagnosis. This choice is called a stoppage rule.

The team wanted to see if ignoring stoppage rules makes autism look less genetic than it really is.

Ignoring stoppage rules pushed the inheritance rate down. When the team fixed the math, the true rate looked higher.

Birth order also looked skewed if stoppage was left out.

Au-Yeung et al. (2015) used the whole Danish registry and found the bias is real but small. Their big sample shows the 1988 warning still matters, yet today’s numbers need only a tiny tweak.

Ohan et al. (2015) gave families fresh risk figures after fixing for stoppage: about 25 % for the next child, jumping to 50 % if two older siblings already have ASD. These hard numbers build directly on the 1988 warning.

Ahlborn et al. (2008) and Castermans et al. (2004) review the same gene-hunt field. Both cite stoppage as a built-in trap, showing the 1988 point became standard textbook advice.

When you read a genetics paper or talk to parents about odds, check if the authors adjusted for stoppage. If they did not, the risk figures are probably too low. Quote the updated 25 % or 50 % numbers from Ohan et al. (2015) instead of the raw rates. This keeps parent expectations and your own clinical picture closer to reality.