Anxiety and depression co-occur so often that some researchers argue they share a common underlying factor. In practice, more than half of people with one meet criteria for the other at some point, and plenty have both simultaneously.
The overlap isn’t only statistical. Poor sleep, difficulty concentrating, irritability, fatigue and restlessness appear in both, which is part of why they’re hard to separate.
Telling them apart
Anxiety is future-facing and activated. Something bad may happen; the system is mobilised. There’s energy in it, unpleasant energy.
Depression is past-and-present-facing and deactivated. Nothing is worth doing; the system is shut down. Anhedonia — the loss of pleasure and interest — is the most specific marker, and it’s the one to ask about.
A useful question: if the anxiety vanished tonight, would you want to do things tomorrow? An anxious person says yes immediately and lists them. A depressed person struggles to name anything.
How each feeds the other
Anxiety produces avoidance. Avoidance shrinks life. A shrunken life produces depression — this is the commonest route, and it’s why treating anxiety early matters.
Depression produces failure and withdrawal, which produces anxiety about performance and about the future. And both wreck sleep, which worsens both.
Which to treat first
The working rule most clinicians use: treat whichever is more impairing, and treat depression first if it is severe.
The reason is practical. Anxiety treatment is mostly behavioural and effortful — homework, experiments, going toward the difficult thing. Severe depression removes the energy and motivation that requires. Asking someone who can’t get out of bed to run exposure homework sets up a failure that they will interpret as further evidence about themselves.
Where depression is moderate, behavioural activation and exposure often run together well, since both involve doing more of what has been avoided — just for different reasons.
The treatments that cover both
CBT has strong evidence for both, and the Unified Protocol was designed specifically as a transdiagnostic treatment for the emotional disorders as a group. ACT also works across both, since the target — the struggle with internal experience — is shared.
On the medication side, SSRIs and SNRIs treat both, which is one reason they’re so widely used here.
The one thing to raise directly
If you’re having thoughts of ending your life, say so to a clinician plainly. The combination of anxiety and depression carries higher risk than either alone, and it’s a specific thing to mention rather than leave for them to ask about.
If you’re in danger now, call or text 988 in the US, or go to an emergency department.