there is a very real tendency of teenagers with anxiety disorders self diagnosing with considerably more stigmatized and impairing mental illnesses (e.g. schizophrenia, DID, personality disorders), but the best response to that isn't to get angry with them for "appropriating" lol. instead you show them coping resources for the problems they're actually having and deemphasize diagnostic categories in general. if an 18 year old is claiming to have alzheimer's, they're probably making an innocent mistake and are in genuine distress. be kind.