This first post may seem at least a bit technical, despite the simplifications. I just want to offer some of the more precise foundations of the approach this blog will discuss. Simpler, more concise posts on mood will follow. I start with an operationalized definition of mood, which I represent as what we really mean when we talk about higher or lower states of affect.
Mood simply represents the sum of the perceived available, temporally discounted net reinforcing options, or the baseline rate of intake of reinforcement, in the context of a required net inake. For example, at a given level of energy expenditure, there is a required net caloric intake. The net intake of this specific category of reinforcer (energy) is translated into mood, which is the ultimate currency in the brain.
Around 80% of people are risk/loss averse, meaning they value losses more heavily than gains. This is increasingly true as mood decreases, because there is the equivalent of the wealth effect operating on the brain. Hence, as mood decreases, net reinforcement shifts toward more immediate, more "profitable" gains, as resource conservation occurs. This is manifest as greater tendencies toward promiscuous behavior, preference shifts toward higher calorie foods (unless body image supresses it), and drug abuse. Also, because the value of losses loom ever greater than that of gains, negative emotional responses are augmented while positive ones are diminished.
This can be summed up nicely here with a greatly simplified, but relevantly complete mathematical expression of net motivation. U = N [ g / ( h + g ) - L / ( h - L )], where U = net utility or net motivation (subjective net expected gain or loss, or you can call this simply demand), g = objective gain, L = objective loss or response cost, h = baseline rate of intake of reinforcement, or "have" (mood), and N = required rate of reinforcement (Need). Ultimately, this is a model relating the required rates of intake of unconditioned reinforcers to the resources perceived available, with the ultimate goal being to optimize inclusive fitness, or reproductive success. This is a reinterpretation of the various matching law models.
This would explain why, for example, girls with relatively higher stress levels actually enter puberty earlier than girls with lower stress. The brain makes an economic calculation based on environmental input indicating an environment relatively hostile to reproductive success, and hence a higher quantity reproductive strategy is selected for. Girls who have higher stress and enter puberty earlier have more sexual partners on average and have sex earlier than those with lower stress levels.
This equation models depression as well, and clearly defines the crux of the problem. Those who are depressed, perhaps seemingly paradoxically, value gains more heavily, but net motivation decreases because the value placed on losses increases at a greater rate as mood decreases. This is consistent with research, demonstrating, for example, that participants diagnosed with depression are willing to expend less energy for reinforcement, but consume more than the non-depressed when response costs are reduced.
Increases in net motivation allow for greater behavioral investment in seeking natural reinforcement, which can lead to habits, with proper psycho-education, that can maintain higher mood levels sans medication. This should be the ulitmate goal of any plan to treat non-purely neurological depression.
This model also predicts that anti-depressants will offer little beneft for the dysthymic, as the curve for net subjective value (utility) flattens as mood increases. This prediction is consistent with experiment and other data. The model also suggests explicit roles for dopamine in mood and motivation, as it represents the subjective magnitude of gains and losses. Hence, the model predicts the inverted U-shaped curve for the effects of stimulants on net motivation, and the effects of stimulants on attention and negative emotional behavior.
This is a self- and externally consistent model of mood, emotions, and motivation. Hopefully, this post can allow one to begin to see where this model comes from. Those wanting more references, or who have any questions about how the dots connect, don't hesitate to ask. This is not extremely complex, but it is a different way of thinking about mood, motivation, thinking, and behavior for many.