Diagnosed mental health patients should receive free prescriptions, Mental illness is considered a disability, Mental heath is far more complex to treat and the medication prescribed can often involve multiple medications.
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Many people diagnosed with mental heath problems can't or don't work therefor their medication can be free but if you are able to work it's not.
Most people with severe mental health problems are not employed, and many people with more common types of mental illness, such as depression, are also not competitively employed.