They are related but distinct, and the distinction matters for how you respond.
Stress is a physiological and psychological response to demand. When you are under pressure, your body mobilises resources: cortisol and adrenaline rise, attention sharpens, motivation to resolve the problem increases. Stress is uncomfortable, but it is functional. It is designed to resolve itself when the pressure eases.
Depression does not resolve when the pressure eases. This is one of the key differences.
How stress can lead to depression
Prolonged or severe stress can tip into depression, particularly when there is no relief in sight, when the stress involves loss or humiliation, or when it overwhelms the person’s capacity to cope. The neurobiological changes associated with chronic stress overlap significantly with those seen in depression: elevated cortisol, disrupted sleep, reduced dopamine activity.
This means that something which starts as a stress response can, over time, become self-sustaining. The stressor may have passed, but the depression persists because it has taken root independently. This is why many people say their depression does not make sense, things are better now, but they still cannot feel it.
The Mental Health Foundation has useful information on the relationship between stress and mental health.
How to tell which one you are dealing with
If your low mood, exhaustion, or inability to enjoy things is tracking a specific stressor and improving when that stressor is absent, you are more likely dealing with stress. If it has become persistent, present regardless of circumstances, and has lasted more than two weeks, it is more likely to be depression. The PHQ-9 screener will help you assess where you sit on the clinical spectrum.
See also how do I know if I am depressed or just going through a hard time? for a more detailed look at this distinction.
What helps for each
For stress, addressing the source (where possible), building recovery time, and maintaining sleep and physical activity are the most effective responses. Mind’s guide to managing stress covers practical approaches.
For depression, or stress that has crossed into depression, the evidence points to structured psychological support, specifically behavioural activation programmes and talking therapies. The WHO’s Step-by-Step programme was developed for exactly this situation: mild to moderate depression in people who do not have easy access to face-to-face care.
Beside delivers this programme free, over WhatsApp, in five sessions with a peer supporter. If you are not sure whether what you are experiencing is stress or depression, you do not need to resolve that question before starting. The programme works for both. Start here.