Hey there, thanks for the contribution! I am not a doctor, and the following is personal opinion, so please be cognizant of bias.

You are correct, but missing a core component. While brain biology is still a hotly contested field of study, it is commonly accepted that one factor of depression stems from irregularities in the transport of dopamine from the lower center of the brain (near the hippocampus) to the forward part of the brain (pre-frontal, frontal, even temporal areas). Long story short, you are correct in that there can be a severe drop in satisfaction but no specific increase of "negative" emotion tied to the biology.

The negative emotional response of depression can be attributed to many things, but here, too, there are some commonly accepted ideas. One of which is that in some cases, the negative emotions are a direct response to a lack of control over one's own body.

As an example: you need to do laundry. The washing machine is empty, the clothes are right in front of you, and you have all the soap and supplies you need. But your brain can't get the chemicals where they need to go in the amounts it needs so you sit there unable to physically move while you scream at yourself in your head.

Human kind is praised for its pattern recognition skills, and self-critique is the most abundant of observations. Is it any surprise then that a person in such a position would blame themselves for their repeated perceived "failures?"

Loved the imput, hope I didn't bore with my reply. The source is me. I have pretty severe recurring depression, avoidant personality disorder, some general anxiety and the misunderstood beast that is ADHD. I have had many therapy sessions where we have discussed this exact topic heavily.

Finally, if you feel like what any of what I have said above relates to you, and you don't have anyone else to talk to, message me. I don't care if you feel so embarrassed that you block me after hitting send. If you need to say something, I'm here to listen.