I would suggest administering a Depression inventory (e.g. Becks, Ham-D) prior to and after a few weeks.  The acute changes you are referring to are very variable.  If there is some irritability associated with depression, this may come out as acute mood changes.  Overall this should improve over time with treatment.

I hope this helps.

I would suggest administering a Depression inventory (e.g. Becks, Ham-D) prior to and after a few weeks.  The acute changes you are referring to are very variable.  If there is some irritability associated with depression, this may come out as acute mood changes.  Overall this should improve over time with treatment.

I hope this helps.

I don't think there is a genuine way to do that because spontaneous fluctuations of mood are too big in such periods of time (e.g. even arousal / time since sleep will play a major role during such periods).  And MDD symptoms by definition should exist for longer time periods (some of them can be measured even just by definition - during longer periods than minutes-hours as you specified)

However, if your intervention is Cocaine or alternatively some anesthetic like Ketamine... (even at low doses) or any other intervention affecting arousal, attention and memory - obviously some effects (e.g. mood) might look greater than spontaneous fluctuations in placebo controls.  The tool would be VAS for mood and perhaps a computerized task like the one used by Diego Pizzagalli from McLean (e.g. Biol Psychiatry. 2006 15; 60: 1147–1154) for reward responsiveness.  BTW, the same group from McLean uses a 6 items VAS when it comes to acute evaluation of mood (e.g. Nat Commun. 2015 Dec 7;6:10065. doi: 10.1038/ncomms10065).

I also suggest a visual-analogue scale. Try the www.emotionthermometers.com for one that includes a depression thermometer and has been validated.