Some attacks or spells may cause damage to an Investigator’s attribute score.
For example, in the module Dead Light, the titular creature has an attack:
Consume (fighting maneuver): If it succeeds it melds inside its victim. The victim suffers 1D10+5 CON damage per turn until dead, dying in agony as deathly light pulses from within their flesh and boils from their eyes and mouth, and the their flesh begins to burn and turn to ash (Sanity roll for viewing the Dead Light consume a victim is 1/1D6 loss).
If the investigator somehow survives this attack, will they ever recover the lost CON from this horrible assault?