The terminology referred to by the Deputy is not used in the Health Act 1970, nor in mental health legislation.
There are references to 'mental handicap' in S.I. No. 277/1971 - Health Services (Amendment) Regulations, 1971 (www.irishstatutebook.ie/eli/1971/si/277/made/en/print ). These Regulations prescribe diseases and disabilities in respect of the Long-Term Illness Scheme, the provision of inpatient services, and the provision of outpatient services.
Applications to receive an LTI Scheme card are made to the Health Service Executive (HSE). The HSE application forms notes that one of the 16 conditions eligible under the LTI Scheme is “Intellectual Disability”, and then notes in parentheses (and in smaller print) how this condition is described in the respective legislation. As such the HSE is working to use appropriate language to describe the condition while also referencing the 1971 legislation/regulation upon which its rests.