The instruction for using the VAMS in this investigation was: "You can answer the following question by placing a cross on the line from 0 to 10: at the moment I feel …"
In other words, the patients are asked for a more or less random impression of their present mood, which is a rather fluctuating thing during the day and during the weeks. I think this is problematic for the following reasons:
1) If all patients would have taken this instruction literal, then their score necessarily would have been only remotely related to whatever other variable because of the fluctuations mentioned above. This weakens the predictive validity of the VAMS.
2) However, each patient may have his own idea of how much time is covered by "at the moment". So a few will think of the last half hour, other ones will think of the last hour, and so on. This is a factor attenuating the standardization of this VAMS.
3) Patients, nowadays, have experience with filling in questionnaires for diagnostic ends, so many of them will understand that it makes little sense to rate their mood for only a short instant. So they do not take the instruction too literal. Some of them will make their rating an expression of the last few days, others of the last week, still others of the last two weeks, and so on. This is another factor attenuating the standardization of this VAMS.
As far as I know the Hamilton equally suffers from the absence of a clear instruction as to the period to be covered by the questions, whereas Beck's Depression Inventory covers explicitly the last two weeks and the Edinburgh Depression Scale (only 10 items!) asks for the last week (Cox et al., 1996).

So it might be interesting to repeat this investigation with clear instructions about the period to be covered by both this VAMS and the parallel test(s) to be used.

Cox, J.L., Chapman, G., Murray D., Jones, P. Validation of the Edinburgh Postnatal Depression Scale (EPDS) in non-postnatal women. Journal of Affective Disorders, 3, 185–9.