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Depression, Cognition, and Value

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Loss of appetite, often coupled with weight loss, is commonly seen in what our medical system defines as depression. It is a diagnostic criterion for a Major Depressive Episode under the DSM-IV. (A Major Depressive Episode is, in turn, the building block for a diagnosis of Major Depressive Disorder.) Spefically, Criterion A3 for Major Depressive Episode is (in the amusingly vague, catch-all language of the DSM-IV):

significant weight loss when not dieting or weight gain (e.g., a change of more than 5% of body weight in a month), or decrease or increase in appetite nearly every day.

(Interestingly, anorexia or significant weight loss, but not weight gain, is a diagnostic subcriterion for what the DSM-IV calls “melancholic features,” a sort of diagnostic hanger-on to Major Depressive Disorder that requires either a loss of pleasure in almost all activities, or a loss of reactivity to usually pleasurable stimuli. People exhibiting melancholic features are less likely to respond to placebo, says the DSM-IV.)

Some depressed people, the DSM-IV tells us, overeat, and some fail to eat enough. For simplicity, and to illustrate an aspect of depressed cognition, I will consider in this essay only the depressed people whose appetite is reduced.

Why do some depressed people not eat? Is there some mysterious “chemical imbalance” that causes both depressed feelings and reduced appetite (except that the same imbalance causes increased appetite sometimes)? Instead of reaching for a possible explanation why someone might not eat, let’s consider the opposite question: why do non-depressed people eat?

A model of the eating-related introspection of a non-depressed person might look like this:

  1. The person feels hungry (or, perhaps more commonly in wealthy countries, the person feels bored).
  2. The person imagines various options for food.
  3. The person picks something that triggers pleasurable associations, based on a hope that eating will produce pleasurable sensations (satiety, aesthetic interest).
  4. The person eats.

People eat to relieve hunger or boredom, in a sense, but the cognitive path followed by a person in order to eat must have some basis in hope – hope that eating will make the person feel better, hope that the action of acquiring food, chewing, and swallowing will be worth it.

A model of the eating related introspection of a depressed person, on the other hand, might look like this (and I’m taking this from introspection, and exaggerating a bit for clarity):

  1. The person feels hungry or bored.
  2. The person, being depressed, also feels miserable.
  3. The person imagines various options for food.
  4. While the person remembers food relieving hunger, the person, if very depressed, also remembers that food does not relieve misery.
  5. No imaginary food seems that much better than any other, since all will ultimately lead to misery (by failing to relieve the misery).
  6. Why bother?
  7. The person may often fail to eat.

Failure to eat by depressed folks has nothing to do with body image, as in eating disorders. It merely has to do with a lack of hope for getting relief from food – and, ultimately, a lack of recognition of the value of eating (distinct from an intention to starve oneself to death).

Despite some evidence for depressive realism, there is some sense in which we might say that the cognition of severely depressed people may be impaired – especially their decision-making capabilities. We might easily say that a person who can’t decide what to eat, and so fails to eat, is indeed cognitively impaired, rather than being especially wise. (I feel rather silly when it happens to me.) In fact, “diminished ability to think or concentrate, or indecisiveness, nearly every day” (emphasis mine) is DSM-IV Criterion A8 for a Major Depressive Episode.

Recent work in cognitive science has explored the role that emotion plays in decision-making. For example, in “The role of emotion in decision-making: Evidence from neurological patients with orbitofrontal damage,” Brain & Cognition 55 (2004) 30–40, Antoine Bechara reports that

The studies of decision-making in neurological patients who can no longer process emotional information normally suggest that people make judgments not only by evaluating the consequences and their probability of occurring, but also and even sometimes primarily at a gut or emotional level. Lesions of the ventromedial (which includes the orbitofrontal) sector of the prefrontal cortex interfere with the normal processing of ‘‘somatic’’ or emotional signals, while sparing most basic cognitive functions. Such damage leads to impairments in the decision-making process, which seriously compromise the quality of decisions in daily life.

That decisions, in humans, are based on emotion is an empirical fact, to the extent that there is evidence for it. People with impaired capacity to experience emotion are not perfect rational calculators; their decisions appear very strange, and often poor. But that is a mere description of our meat-based decision-making apparatus. It says nothing as to how the best decisions might be made – or, most importantly, what characteristics distinguish the best decisions. To specify that, we need to know what is valuable – for values must be the ultimate criteria for which decisions are good, and which poor. Why do anything? Here psychology must collide with philosophy.

To the extent that a depressed person does not make a normal decision – including the silly case of failing to eat (for lack of a compelling reason, not for lack of resources) – the depressed person is merely revealing his values. To claim that the depressed person is cognitively impaired in a way that would justify intervention into his decisions is to say that his values are incorrect, or that he is not justified in pursuing his values, and should be required to pursue our values instead. We cannot, I think, ethically intervene (force-feed) when a hunger striker decides that she values, say, women’s suffrage over the continued satisfaction of her hunger, even unto death. When a depressed person concludes that nothing is valuable, except perhaps an end to suffering, we are in no better ethical position to intervene – either to force-feed, or to withhold the means for suicide.

Depressed people who overeat are consistent with my model. These people – less severely depressed, perhaps – have not completely given up on food as a source of relief, and may in fact clearly remember receiving positive feelings as a result of food. Therefore, instead of triggering the “eat” response every time one is hungry or bored, the overeating depressed person triggers it in addition every time he feels miserable, leading to increased eating and perhaps weight gain. As I pointed out above, increased appetite is not a feature associated with “melancholic features,” which might, in a vague sense perceptible from the DSM-IV report on response to placebo, indicate a more severe type of depression. This is consistent with overeaters being less “hopelessly” depressed than undereaters.

Written by Sister Y

June 2, 2008 at 5:57 am

Is Depression Adaptive? And Does It Matter?

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Evolutionary biology theorists have hypothesized in recent years that depression may be an adaptive trait, that is, one that confers an evolutionary benefit. Watson and Andrews, in their paper “Toward a revised evolutionary adaptationist analysis of depression: the social navigation hypothesis,” published in the Journal of Affective Disorders, have hypothesized as follows:

First, depression induces cognitive changes that focus and enhance capacities for the accurate analysis and solution of key social problems, suggesting a social rumination function. Second, the costs associated with the anhedonia and psychomotor perturbation of depression can persuade reluctant social partners to provide help or make concessions via two possible mechanisms, namely, honest signaling and passive, unintentional fitness extortion. Thus it may also have a social motivation function.

As with many evolutionary psychology hypotheses, there is little empirical support. Observers note that depression is highly prevalent, that it occurs with high frequency even among individuals with high reproductive value, and that it may provide a fitness advantage in certain conditions, such as providing a more accurate assessment of the circumstances (see depressive realism) or providing a convincing signal that the individual needs more support from the group. (Of course, depression is often detrimental to fitness, including reproductive fitness.) The theory that depression is adaptive is interesting; however, it is generous to claim that the evidence for this hypothesis is even weak. It is almost nonexistent.

The more interesting question for my purposes is, if we concluded that depression is an adaptive trait and provided a fitness benefit in our environment of evolutionary adaptation, should this influence our view of the right to suicide? It seems clear that it should not.

If depression is adaptive, that means that the depressed state is a normal, expected part of human life, which conferred a benefit on our ancestors. This hypothesis says nothing about whether people defined as depressed should be forcibly prevented from committing suicide. In fact, if we suppose that depression confers an increase in rationality, we should be even more inclined to respect the depressed person’s analysis of his situation, and his decision to commit suicide.

Aside from rationality, the fact that depression may be evolutionarily adaptive would imply that much of our suffering is “by design” – that is to say, part of the evolutionary package. It would be yet another biologically-determined limit on human happiness, and entitle us all the more to refuse to participate in the project of life.

The interesting implication of one hypothesis for the evolutionary adaptiveness of depression has to do with treatment: the idea that people become depressed as a way to credibly signal that they need more support from their group than they are getting. An implication of this would be that depression could be treated by providing depressed people with more “support” (whatever that might mean). It is an interesting hypothesis, but, again, does not provide a compelling reason for prohibiting suicide. First, there is no evidence that any method of treating severe depression is widely effective. Even placebos are much less effective at treating severe depression than at treating moderate or mild depression (meaning severe depression rarely spontaneously improves, and does not respond to sham treatment). Widely prescribed anti-depressants are almost as useless. If some form of “group support” were shown to reliably treat severe depression, that would be wonderful news – but a right to suicide would still be warranted for those who still wish to die despite having submitted to this treatment (or, I would argue, despite refusing this treatment).

I hope to address the question of when, if ever, paternalism is appropriate when dealing with depression and suicide in a later post. I thank reader Mike Kenny for the interesting questions that I’m addressing here.

Written by Sister Y

May 14, 2008 at 9:20 pm

Qualia of Happiness

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Robin Hanson on Overcoming Bias recently posted links to data that religious people and people holding conservative political beliefs report being happier than heathen liberals. There was much debate over whether this should mean we should adopt conservative outlooks, and whether seeking truth was an inherent value even if it meant being less happy, but my problem is with the data: it is all based on self-report.

I am willing to go along with the idea that we have an a priori reason to believe a statement just because the statement is made up of language whose sense we can understand. So, if there were no further evidence, we would be justified in believing the self-reports of happiness. But, in this context, there is a custom of members of this group lying about this particular fact (happiness) – that is, the evangelical Christian custom of “witnessing,” which entails acting happy and rich and perfect so that pagan nonbelievers may see how happy Christianity makes one. Conservative social movements such as Amway also encourage false displays of wealth and happiness. We have reason to question the sincerity of these self-reports of happiness.

But even if we allow the sincerity of these self-reports of happiness, we may still question their validity. It is extremely difficult to make an accurate overall evaluation of one’s happiness. In fact, the tendency is to overstate one’s happiness, a phenomenon known as the optimistic bias. Depressed people are far more accurate than non-depressed people in making predictions about the future based on evidence, a phenomenon known as depressive realism. Given the tendency toward unjustified optimism, we should doubt not only the self-reports of conservatives and the religious, but of all people who report happiness.

But, of course, how can we get at happiness if not through self-reports? Would it be ludicrous to try to develop some cheap and tasty qualia of happiness, or even qualia of suffering, which might be easier to measure? Wakefulness is often used as a proxy for consciousness where consciousness can’t be reported (as with fetuses). Could there not be an objectively observable proxy for happiness that could be demonstrated to be so closely correlated with happiness that we’d trust it over a self-report?

As noted, suffering may be easier to measure objectively than happiness. Suicide rates may give an objectively verifiable estimate of the unhappiness in a given population. Do social conservatives kill themselves less frequently than liberals? However, given the importance of happiness both as an end, and of measuring happiness to figure out which policies might increase it, qualia of happiness seem to be worthy things to locate.

I am not necessarily defining happiness as temporary positive affect, although positive affect might be part of the calculation.

Written by Sister Y

May 12, 2008 at 9:31 pm