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Some depressed patients complain bitterly of profound memory loss and other cognitive symptoms. As these are secondary to the emotional disorders, they constitute a pseudodementia and not a true dementia.

Both depression and dementia share many common symptoms such as forgetfulness, poor concentration, lack of motivation and loss of interest.
Several factors may explain why some depressive patients show cognitive abnormalities. These can be due to personal predisposition, activation of hysterical mechanisms, cerebral metabolic abnormalities, changes in level of arousal and as a part of the general of psychomotor retardation.

The ageing process affecting the brain such as the neuronal loss may combine with the neurochemical changes in depression and lead to cognitive failure. It is these chemical and physiological alternations which are responsible for both depression and the cognitive changes. Therefore, this syndrome should be considered to be organic in origin and should be labeled as dementia of depression rather than pseudodementia.

Table No. 1 shows the differences between true dementia and the dementia of depression (Pseudodementia).

Between Pseudodementia and Dementia*

Anxiety and depression can adversely affect intellectual and adapting functions of the patient with dementia. It is important to treat these problems. The anxiety and confusion are especially more obvious at night. The insomnia and restlessness may also be produced by aches and pains and simple analgesics may be preferable to hypnotics.

Barbiturates should be avoided as they can cause confusion and depression. Chloral hydrate 500 mg, diphenhydramine 25 mg and promethazine 10 to 25 mg are useful hypnotics in demented depressives.

Short acting benzodiazepines like lorazepam 0.5 to 2 mg or alprazolam 0.25 to 1.5 mg are better than long acting drugs like diazepam as there is less risk of accumulation. For motor agitation, small doses of neuroleptics like haloperidol 0.25 mg or thioridazine 10 to 25 mg can be used. Haloperidol has the least action on autonomic lability. Used antidepressants are trazadone,
nortriptyline, dothiepin, etc. It must be remembered that the geriatric doses of most psychotropic drugs are close to the paediatric doses and it is advisable to start treatment with the lowest possible dose.

Most neuroleptics and antidepressants have anticholinergic side- effects. There is an acetylcholine deficiency in Alzheimer's dementia and drugs with high anticholinergic side-effects can be detrimental. In patients with prostatic enlargement or glaucoma, these side-effects can cause urinary retention or increase in the intraocular tension.

Dothiepin is an effective antidepressant with anxiolytic action and has lesser anticholinergic side-effects. An added advantage of dothiepin is that it also has sedative action which helps when sleep disturbances occur in depression.

Hypnotics and tranquilizers can be used on an SOS basis, but antidepressants should be administered daily for several weeks or months.As there is a degeneration of the nerve cells in dementia, drugs which increase cerebral blood flow like cyclospasmol, pyritinol or piracetam are not useful. Most recently, drugs which alter acetylcholine transmission are undergoing trials. To date their usefulness is not convincingly established.