CoGNiTiVe iMpAirMeNT iN pArKiNSoN ’ S diSeASe

To The ediTor We would like to comment some methodological issues that arised from the interesting paper of Piovesan et al. and that did not were cleared in the discussion. As it is known, many antiparkinsonian agents may cause cognitive and psychiatric symptoms, mainly those with anti-cholinergic effects. Piovesan et al. stated that none of the patients in the PWID group (Parkinson Group with depression) were taking medication with a potential anticholinergic effect, but did not mention anything about the parkinson group without depression (PWOD). If PWOD was taking anti-cholinergic drugs, this may have biased some results found in the paper, such as those stated here: a) “comparison of individuals with and without depression did not reveal any statistically significant data that indicated that depression could have an influence on cognitive function in this group”. In other words, parkinsonian patients with depression may have similar cognitive performance just when compared with parkinsonian patients without depression but using anti-cholinergic agents, what will naturally impair the real cognitive potential performance of PWOD group. b) “the PG group as a whole, rather than just those individuals whose scores indicated that they were depressive, had more obvious cognitive deficits than the CG group”. Once more, use of anti-cholinergic drugs may have biased this statement. Besides that, another antiparkinsonian drugs (excluding this time the anti-cholinergic ones) may cause cognitive and psychiatric symptoms, including depression, thus explaining, at least in part, some discrepancies between the prevalence of depression in the parkinsonian group when compared with controls. Another important issue is that some psychiatric side effects (sleep disturbance, inapetence, concentration difficulties, disturbed thoghts) of dopaminergic agents may score and contribute to higher pontuations on Montgomery-Asberg scale in Parkinson’s Disease (PD). Finally, we would like to comment on the difficulties related to the diagnosis of depression in PD. Because features of PD frequently overlap with typical manifestations of major affective disorder (or mild dysthymia), diagnosis of this comorbidity is challenging. Some of these interactive features include cognitive and speech deficits and impairments in emotional expression (e.g., PD-related facial masking) or processing. Apathy as well can be extremely difficult to distinguish from depression in PD.