This is a standard question in therapy or psych assessment intakes, though the wording changes depending on the situation. We know that many mental health issues like anxiety, depression, bipolar disorder, and schizophrenia have a genetic component, and so do other neurodivergences like ADHD and autism. If we know our family history, we can better narrow down what diagnosis might explain difficulties someone is having now.
But our understanding of how our minds work has changed over time. Disruptive Mood Dysregulation Disorder, for example, wasn’t recognized in the Diagnostic and Statistical Manual of Mental Disorders until 2013. A child with these symptoms may have family history, but it would be impossible for the parents to be diagnosed in childhood because the diagnosis did not exist.
(The symptoms and the disorder existed, of course; we just called it other things, like childhood-onset bipolar disorder.)
The first American to ever be diagnosed as autistic is still alive, and our diagnostic understanding of autism is still very limited, causing many to be misdiagnosed or overlooked. So, if there is “no family history” of autism, does that mean it was not there, or does that mean no one was evaluated, or their behaviors were never conceptualized that specific way?
Or maybe a teacher or doctor recognized those traits, but their parents did not want them “labeled” (a valid concern in light of how terrible the stigma around these diagnoses still is!), did not think the issues were severe enough to warrant intervention, or thought, “That’s not a diagnosis! I do that too” (you know, because it’s genetic).
If you don’t have a known family history of a diagnosis, that does not invalidate your experience! Genetics are not everything – our interaction with the environment also informs how our brains develop. Besides, maybe you are just the first to label your experience this way.