omgdougless,

Welcome to NeuroTalk.

Nobody can say whether walking into a 2x4 would cause a concussion.

What immediate symptoms did you manifest?

If the 2x4 was loose and moved when you bumped it, I can't imagine the impact had any substantial force.

It was startling, for sure. A startle response can be quite upsetting but not indicative of an injury.

Why does it matter? Will you behave differently if you are told it was not a concussive force vs a concussive force?

The rule is quite simple. You treat the symptoms, not the impact.

Treat your anxiety. If you know you struggle with anxiety, that should be your first concern. Anxiety can cause almost every symptom of a concussion. A startle is usually an anxiety trigger.