Why does my dog destroy things only when I leave?

Before assuming anxiety, check whether the destruction is genuinely limited to your absences or whether the dog also chews or digs when you are home but distracted, since the latter points more toward general boredom or insufficient exercise than true separation distress.

Damage focused on a specific door, the frame around it, or a window the dog can see out of suggests the behavior is connected to trying to leave or watch for you, which is a strong indicator of separation related distress rather than random mischief.

Start recording short absences to see how quickly the destructive behavior begins, since distress that starts within the first few minutes needs a structured desensitization plan, ideally with a qualified behaviorist, rather than more exercise or scolding, which does not address the underlying fear.

Scolding a dog for destruction discovered after you return does nothing to address behavior that happened potentially hours earlier, since dogs do not connect a delayed consequence with the original action, and this approach can add general anxiety about your return without touching the actual cause. Managing the environment to prevent damage while addressing the underlying distress directly produces far better results than any punishment based approach. Focusing energy on prevention, through a safer space and shorter absences while training progresses, tends to reduce an owner's own frustration too, which in turn makes the whole household calmer around the issue.