There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

W. Wilson's (1967) review of the area of subjective well-being (SWB) advanced several conclusions regarding those who report high levels of "happiness". A number of his conclusions have been overturned: youth and modest aspirations no longer are seen as prerequisites of SWB. E. Diener's (1984) review placed greater emphasis on theories that stressed psychological factors. In the current article, the authors review current evidence for Wilson's conclusions and discuss modern theories of SWB that stress dispositional influences, adaptation, goals, and coping strategies. The next steps in the evolution of the field are to comprehend the interaction of psychological factors with life circumstances in producing SWB, to understand the causal pathways leading to happiness, understand the processes underlying adaptation to events, and develop theories that explain why certain variables differentially influence the different components of SWV (life satisfaction, pleasant affect, and unpleasant affect).

Subjective Well-Being: Three Decades of Progress

W Wilson's (1967) review of the area of subjective well-being (SWB) advanced several conclusions regarding those who report high levels of "happiness" A number of his conclusions have been overturned: youth and modest aspirations no longer are seen as prerequisites of SWB E Diener's (1984) review placed greater emphasis on theories that stressed psychological factors In the current article, the authors review current evidence for Wilson's conclusions and discuss modern theories of SWB that stress dispositional influences, adaptation, goals, and coping strategies The next steps in the evolution of the field are to comprehend the interaction of psychological factors with life circumstances in producing SWB, to understand the causal pathways leading to happiness, understand the processes underlying adaptation to events, and develop theories that explain why certain variables differentially influence the different components of SWB (life satisfaction, pleasant affect, and unpleasant affect) In 1967, Warner Wilson presented a broad review of subjective well-being (SWB) research entitled, "Correlates of Avowed Happiness" Based on the limited data available at that time, Wilson concluded that the happy person is a "young, healthy, welleducated, well-paid, extroverted, optimistic, worry-free, religious, married person with high self-esteem, job morale, modest aspirations, of either sex and of a wide range of intelligence" (p 294) In the three decades since Wilson's review, investigations into SWB have evolved Although researchers now know a great deal more about the correlates of SWB, they are less interested in simply describing the demographic characteristics that correlate with it Instead, they focus their effort on understanding the processes that underlie happiness This trend represents a greater recognition of the central role played by people's goals, coping efforts, and dispositions In this article, we review research on several major theoretical approaches to well-being and then indicate how these theories clarify the findings on demographic correlates of SWB Throughout the review we suggest four directions that researchers should pursue in the decades ahead These are by no means the only questions left to answer, but we believe they are the most interesting issues left to resolve First, the causal direction of the correlates of happiness must be examined through more sophisticated methodologies Although the causal priority of demographic factors such as marriage and income is intuitively appealing, it is by no means certain Second, researchers must focus greater attention on the interaction between internal factors (such as personality traits) and external circumstances As we shall see, demographic factors have surprisingly small effects on SWB, but these effects may depend on the personalities of those individuals being studied Thus, future research must take Person X Situation interactions into account Third, researchers must strive to understand the processes underlying adaptation Considerable adaptation to both good and bad circumstances often occurs, yet the processes responsible for these effects are poorly understood Research that examines how habituation, coping strategies, and changing goals influence adaptation will shed much light on the processes responsible for SWB Finally, theories must be refined to make specific predictions about how input variables differentially influence the components of SWB In the past, many researchers have treated SWB as a monolithic entity, but it is now clear that there are separable components that exhibit unique patterns of relations with different variables In each section of this article we discuss progress and opportunities in these four areas

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Subjective well-being: Three decades of progress

Whole brain segmentation: automated labeling of neuroanatomical structures in the human brain.

Depression is less prevalent among older adults than among younger adults, but it can have serious consequences. More than half of cases represent a first onset in later life. Although suicide rates in the elderly are declining, they are still higher than in younger adults and are more closely associated with depression. Depressed older adults are less likely to endorse affective symptoms and more likely to display cognitive changes, somatic symptoms, and loss of interest than are depressed younger adults. Risk factors leading to the development of late-life depression likely comprise complex interactions among genetic vulnerabilities, cognitive diathesis, age-associated neurobiological changes, and stressful events. Insomnia is an often overlooked risk factor for late-life depression. We suggest that a common pathway to depression in older adults, regardless of which predisposing risks are most prominent, may be curtailment of daily activities. Accompanying self-critical thinking may exacerbate and maintain a depressed state. Offsetting the increasing prevalence of certain risk factors in late life are age-related increases in psychological resilience. Other protective factors include higher education and socioeconomic status, engagement in valued activities, and religious or spiritual involvement. Treatments including behavioral therapy, cognitive-behavioral therapy, cognitive bibliotherapy, problem-solving therapy, brief psychodynamic therapy, and life review/reminiscence therapy are effective but are too infrequently used with older adults. Preventive interventions including education for individuals with chronic illness, behavioral activation, cognitive restructuring, problem-solving skills training, group support, and life review have also received support.

Depression in Older Adults

ronmentalinfluences,adjustingforage,werederivedfrom the twin data. Results: Heritability for AD was estimated to be 58% in the full model and 79% in the best-fitting model, with the balance of variation explained by nonshared environmental influences. There were no significant differences between men and women in prevalence or heritability after controlling for age. Within pairs concordant for AD, intrapair difference in age at onset was significantlygreaterindizygoticthaninmonozygoticpairs,suggesting genetic influences on timing of the disease. Conclusions: In the largest twin study to date, we confirmed that heritability for AD is high and that the same genetic factors are influential for both men and women. However, nongenetic risk factors also play an important role and might be the focus for interventions to reduce disease risk or delay disease onset. Arch Gen Psychiatry. 2006;63:168-174

https://jamanetwork.com/journals/jamapsychiatry/articlepdf/209307/YOA40625.pdf

Role of Genes and Environments for Explaining Alzheimer Disease

Positive and negative affect, measured by the Bradburn Affect Balance Scale, were studied in a longitudinal sample spanning from 1971 to 1994. The sample (N = 2,804) represented 4 generations of families. Linear trend analyses compared generations over time for positive and negative affect and also examined the possible influences of neuroticism and extraversion on initial levels of affect and patterns of change in affect. Negative affect decreased with age for all generations, although the rate was attenuated among the oldest adults. Higher neuroticism scores also attenuated the decrease in negative affect across time. For positive affect, the younger and middle-aged adults showed marked stability, but the older group evidenced a small decrease over time. Higher levels of extraversion were related to more stability in positive affect.

/pdf/age-related-differences-and-change-in-positive-and-negative-3713jdm4gc.pdf

Age-related differences and change in positive and negative affect over 23 years.

OBJECTIVE: Substantial evidence supports the heritability of lifetime major depression. Less clear is whether genetic influences in major depression are more important in women than in men and whether genetic risk factors are the same in the two sexes. It is not known whether genetic effects on major depression are constant across historical cohorts. METHOD: Lifetime major depression was assessed at personal interview by modified DSM-IV criteria in 42,161 twins, including 15,493 complete pairs, from the national Swedish Twin Registry. Twin models were evaluated by using the program Mx. RESULTS: Model fitting indicated that the heritability of liability to major depression was significantly higher in women (42%) than men (29%) and the genetic risk factors for major depression were moderately correlated in men and women. No significant differences were seen in the etiologic roles of genetic and environmental factors in major depression in three cohorts spanning birth years 1900–1958. CONCLUSIONS: In the lar...

https://ajp.psychiatryonline.org/doi/pdf/10.1176/appi.ajp.163.1.109

A Swedish national twin study of lifetime major depression.

Context Prior studies suggest that the personality traits of neuroticism and extroversion may be related to the liability to major depression (MD). Objective To clarify the magnitude and nature of the association between neuroticism and extroversion and the risk for MD. Design Longitudinal population-based twin cohort. Setting General community. Participants A total of 20 692 members of same-sex twin pairs from the population-based Swedish Twin Registry who completed a self-report questionnaire assessing neuroticism and extroversion in 1972 and 1973 and were personally interviewed for lifetime history of MD more than 25 years later. Main Outcome Measure Lifetime history of modifiedDSM-IVMD. Results Levels of neuroticism strongly predicted the risks for both lifetime and new-onset MD. Twin modeling indicated that the association between neuroticism and MD resulted largely from shared genetic risk factors, with a genetic correlation of +0.46 to +0.47. Levels of extroversion were weakly and inversely related to the risks for lifetime and new-onset MD. This effect disappeared when we controlled for the level of neuroticism. Twin modeling produced similar results. Conclusions Results from both longitudinal and genetic analyses support the hypothesis that neuroticism strongly reflects the liability to MD. This association arises largely because neuroticism indexes the genetic risk for depressive illness. However, substantial proportions of the genetic vulnerability to MD are not reflected in neuroticism. By contrast, extroversion is only weakly related to risk for MD.

https://jamanetwork.com/journals/jamapsychiatry/articlepdf/209887/yoa60015.pdf

Margaret Gatz

Papers

Depression in Older Adults

Role of Genes and Environments for Explaining Alzheimer Disease

Age-related differences and change in positive and negative affect over 23 years.

A Swedish national twin study of lifetime major depression.

Personality and major depression: a Swedish longitudinal, population-based twin study.