A functional deficiency of cholinergic neurotransmission may cause the HPA axis hypoactivity seen in CFS since cholinergic activity potentially stimulates the HPA axis.25 Sleep disturbances are common in patients with CFS and may be due to a central cholinergic deficiency.26 Galantamine hydrobromide is a selective acetylcholinesterase inhibitor. Here, ACHE is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.