Does severe chronic depression and mental illnesses remove religious obligations?

The illness of depression is treated by strengthening faith and [reciting] invocations (dhikr). Religious obligations do not fall away from the person afflicted by it as long as they possess their intellect. Thus, they must perform these obligations to the best of their ability, based on the Almighty’s saying: "So fear Allah as much as you are able." However, if their condition reaches the point of losing their intellect, then the obligations fall away from them, based on the Prophet’s (peace be upon him) saying: "The pen has been lifted from three: from the sleeper until he awakens, from the child until he reaches puberty, and from the insane person until he regains his sanity."