One must distinguish between “sloth” the deadly sin and say depression…
So on one hand one has say a emotional disorder and on the other hand one has that which is a sin.
Depression per se does not = sloth.
Now as to the term “deadly”
To borrow from my previous post:
The term “deadly” --often confuses persons.
Such is simply not the case that deadly sins/capital sins = grave matter .
For example --the chief of them is Pride. Pride yes can be grave matter --like a person says I do not need God. But often in the life of say a Christian it is venial matter (sinning in pride in other ways…)
Anger can be grave matter – like for example --when one is deliberately angry -seeking to say seriously harm someone.
Or seriously wounding charity or justice…
But often it can be venial in life. One gets a little angry that something did not go the way one wanted…etc
or take gluttony – individual acts of such by way of intemperance are often venial in nature.
Though for example one can have grave matter --for example getting drunk where one looses ones reason…etc.
So no it is not a simple: Deadly sins -Capital sins = grave matter.
Of course sins under lust – like fornication, lusting after some woman, adultery etc do not admit of parvity of matter.
A better term is “capital sins”. They are called Capital cause they are the “head” capitus of many other sins that they engender…(and deadly cause yes the seven can be deadly…)
But the term used more so today is capital sins.
Catechism:
1866 Vices can be classified according to the virtues they oppose, or also be linked to the capital sins which Christian experience has distinguished, following St. John Cassian and St. Gregory the Great. They are called “capital” because they engender other sins, other vices. They are pride, avarice, envy, wrath, lust, gluttony, and sloth or acedia.
scborromeo.org/ccc/ccc_toc.htm
- What are vices?
1866-1867
Vices are the opposite of virtues. They are perverse habits which darken the conscience and incline one to evil. The vices can be linked to the seven, so-called, capital sins which are: pride, avarice, envy, anger, lust, gluttony, and sloth or acedia.
vatican.va/archive/compen…um-ccc_en.html