[zug_zug]

I guess then my thought is that whether it's one disorder or 4 or any number perhaps is best understood as a statistical question.

For example, if a parent exhibit autism symptom X (e.g. trouble understanding emotions), are there kids more likely to inherit symptom X, or ANY autism symptom.

If X is uniquely heritable, then perhaps it's best as multiple disorders. But if X leads equally likely to X, Y, or Z then it's better understood as one disorder.