does taking psychiatric medication prevent harvest?

[Infinite]

I thought intelligent infinity was the passport to the next Octave, not the next density, according to Ra.

Ra used the word "octave" to refer to the 7 densities as a whole or to a density individually.

This says "leaving of the density" not "going into 4D".

Leaving our density means going to the fourth (with the exception of the Wanderers, of course). The evolution work is constant. Each entity exists at the level at which it comfortably supports.

So anyone who harvests themselves is negative?

No. Being harvested or harvest yourself are possibilities of both polarities.