Grief and clinical depression overlap in their most visible features: low mood, poor sleep, loss of appetite, withdrawal. Clinicians still treat them as different things, and the reasons are specific.
The distinction is about pattern, not intensity
Severe grief can be more painful in a given moment than a depressive episode. Intensity is therefore not the dividing line.
What differs is the structure of the distress over hours and days, and how the person describes their own situation while inside it.
Those two features are what a clinical assessment is examining.
Grief tends to arrive in waves
Grief characteristically comes in surges, often triggered by a reminder such as a place, an object or a date, with intervals of comparative relief between them.
Positive feeling remains reachable inside those intervals. People who are grieving can be absorbed by company or humour, then return to sorrow.
Depressed mood is described more often as continuous and unresponsive, with the flat quality persisting through circumstances that would ordinarily lift it.
Self-regard usually stays intact in grief
A grieving person's thoughts are largely occupied with the person or thing lost. Self-criticism, where it appears, tends to attach to specific regrets about the loss.
Depression more often carries generalised worthlessness: a judgement about the self as a whole, independent of any event.
This difference in the content of thought is one of the more useful signals available to an assessor, because it is not visible from behaviour alone.
Time course is assessed rather than assumed
Grief typically softens in frequency and intensity, though unevenly and often over a long period, with anniversaries producing renewed surges.
Distress that stays fixed at the same level, or deepens rather than fluctuating, is the pattern that prompts closer assessment.
Diagnostic systems have gone back and forth on how bereavement should interact with a depression diagnosis, which reflects genuine difficulty rather than indecision.
The distinction exists because it changes the response
Separating the two matters because the appropriate response differs. Grief is generally supported rather than treated, while a depressive episode may call for specific clinical intervention.
Neither judgement is reliably made from the outside or from a checklist. Persistent hopelessness, or any thought of self-harm, is a reason to contact a doctor or a crisis service without waiting to work out which category applies.