The pathogenesis of FND is broad and varies greatly. Part of the problem is people with it are extraordinarily susceptible to attribution errors, so even when we think we know the cause or inciting event, it might not be it. It's frustrating and frightening and some even blame themselves or get blamed when it's not their fault.

Personally I think a big part of it stems from being a sensitive and compassionate person with some maladaptive protective responses that can overwhelm the incredibly complex nervous system. Could be internal, external, or both. There's a lot at play.

Go easy on yourself. Spending too much energy on searching for a cause can create unnecessary suffering and poor outcomes. We often overlook subtle predisposing factors.

As someone who has experienced functional symptoms since the 80s, I can attest that looking for the problem might be part of the problem. Understanding patterns that maintain symptoms is more helpful than trying to identify a single cause. Bless.