The aetiology of Alzheimer's disease and senile dementia of the Alzheimer type (AD/SDAT) are unknown, and primary prevention is thus infeasible. As overactivity in the hypothalamic-pituitary-adrenal axis (possibly indicating maladaptation to stress) and vitamin B-12 deficiency are common, secondary prevention should focus on stress and dietary factors. Nerve growth factors and ganglioside GM1 have been used to inhibit progression of the disorder, but this treatment is still at an experimental stage, as are efforts to prevent the formation of amyloid. Breakthroughs in AD/SDAT treatment have been seen in trials with supplementation of neurotransmitter deficits. Tacrine, a drug that inhibits acetylcholinesterase, has proved to have a cognitive-enhancing effect, but this is limited in time and the drug has side-effects. Selective serotonin reuptake inhibitors have a proven effect on the emotional disturbances seen in AD/SDAT.