Chastity and orgasm denial discussion

My partner has been wearing his lock almost constantly since December 1st. It is the longest period he has stayed locked without any breaks, as we have only started a serious chastity journey from that day on. Previously, it was usually a few days in and out, with him holding onto the key so he could decide when to use it (which isn’t true anymore!). Since our initial lock up, he has been permitted to cum around three or four times and got one night off without his device. I know many couples go much longer than this, but we are still building towards that goal because he clearly loves being allowed to cum, and I love watching him enjoy it. We have noticed that the few occasions when he does cum, he seems to enter a short period (perhaps half a day) of what I would describe as a ‘grumpy’ mood compared to his usual self. My boyfriend is normally very laid-back, happy, and content. During this time we notice some irritability and just generally lower spirits. It tends to fade shortly after it appears, and he returns to normal moods quickly. After that, he enters a more heightened horny state (which I adore) before settling back into his usual rhythm. We are both wondering if the mood drop others have written about is actually real, or if it might just be a placebo effect with another cause? For instance, could lack of sleep be responsible instead, and its occurrence after he came was merely coincidental? What do you all think about this subject? Is there any scientific evidence for it? Also, if the mood drop is genuine, does it always happen? Or is it just something he is going through as an adjustment to our new, increased level of chastity? Thank you in advance for your advice!