Overview of this block

F70 Mild mental retardation

F71 Moderate mental retardation

F72 Severe mental retardation

F73 Profound mental retardation

F78 Other mental retardation

F79 Unspecified mental retardation

	A fourth character may be used to specify the extent of associated
	behavioural impairment:
		F7x.0 No, or minimal, impairment of behaviour
		F7x.1 Significant impairment of behaviour requiring
			attention or treatment
		F7x.8 Other impairments of behaviour
		F7x.9 Without mention of impairment of behaviour