https://icd.who.int/.../2016/en#/F06.4
F06.4Organic anxiety disorder
A disorder characterized by the essential descriptive features of a generalized anxiety disorder (F41.1), a panic disorder (F41.0), or a combination of both, but arising as a consequence of an organic disorder.
Excl.:
anxiety disorders, nonorganic or unspecified
Organic Disorder
An organic disease is one caused by a physical or physiological change to some tissue or organ of the body. The term sometimes excludes infections. It is commonly used in contrast with mental disorders. It includes emotional and behavioral disorders if they are due to changes to the physical structures or functioning of the body, such as after a stroke or a traumatic brain injury, but not if they are due to psychosocial issues.
Note - To simplify an organic disorder usually refers to a condition caused by damage to the body. Things like head injuries, strokes, gun shots, etc but not usually used to describe damages due to stress, chemical effects, effects of drugs, etc.
Clear as mud right?