BDNF is a critical mediator of vulnerability to stress, memory of fear/trauma, and stress-related disorders such as post-traumatic stress disorder.^[92]

Variants close to the BDNF gene were found to be associated with obesity in two very large genome-wide association studies of body mass index (BMI).^[93][94]

High levels of BDNF and Substance P have been associated with increased itching in eczema.^[95]

BDNF is a regulator of drug addiction and psychological dependence. Animals chronically exposed to drugs of abuse show increased levels of BDNF in the ventral tegmental area (VTA) of the brain, and when BDNF is injected directly into the VTA of rats, the animals act as if they are addicted to and psychologically dependent upon opiates.^[77]

BDNF is a short-term promoter,^[96] but a long-term inhibitor of pain sensitivity, as a result of its effect as inducer of neuronal differentiation.^[97] The polymorphism Thr2Ile may be linked to congenital central hypoventilation syndrome.^[98][99] BDNF and IL-6 might be involved in the pathogenesis of post-chemotherapy cognitive impairment (PCCI, also known as chemo brain) and fatigue.^[100]

https://en.wikipedia.org/wiki/Brain-derived_neurotrophic_factor