How have the courts interpreted the term "mental illness" in section 232 of the Mental Health Act?

Next, the father argues that the term "mental illness" as used in section 232, subdivision (a)(5), is so vague that its meaning cannot be determined, citing Lanzetta v. New Jersey (1939) 306 U.S. 451, 458, 59 S.Ct. 618, 621, 83 L.Ed. 888. For example, under the statute, mental illness could be declared under the definition which is used by any court of competent jurisdiction, wherever situated. Mental illness could also be found for any reason--incompetency to make a contract, etc. This argument fails for a number of reasons.