There is no such thing as mental illness, except in a metaphorical sense. The same is true for mental health. It does not literally exist.
The literal ideas of mental health and mental illness are literalized metaphors. Literalizing metaphors has undesirable unintended consequences.
Thinking in terms of subjective emotional well being and subjective emotional distress is much more linguistically accurate and useful.
If there is no such thing as mental illness, then there is no such thing as mental health either.
The mind is abstract so it cannot be literally sick nor literally well. It only can in a metaphorical sense. Don't literalize metaphors, because that will have unintended consequences.
As a being with emotions, you can experience distressing emotions and feelings. You can experience emotional well being. You can have bad habits that are emotionally distressing. You can experience misery and personal tragedy. You can engage in behaviors that are helpful or harmful to your self.
Is medicalizing emotions, thoughts, and behaviors authentically helpful to anyone? Ultimately, probably not in most all circumstances.
Possibly most psychiatric drugs rely heavily on placebo effects. Psychiatric drugs might actually worsen longterm outcomes in many circumstances.
The book Anatomy of an Epidemic by Robert Whitaker explores how pharmaceutical companies hide a significant number of studies that show their drugs don't really work and selectively publicizes the ones that show that psychiatric drugs may be effective. Don't believe it? Read the book.