Emotional expression, or “affect,” covers a range of temporal domains. There are “emotions,” moment-to-moment fluctuations which, while intensely experienced, come and go within minutes. When a given emotional state lasts longer – hours, days, or months – it is described as “mood.” Finally, there is “temperament,” a lifelong emotional disposition considered to be part of one’s constitutional makeup (1). When temperament manifests as “affective” – that is to say, appears as a similar but less severe variant of a disordered mood state – things start to get interesting.
How common are affective temperaments? Affective temperaments are thought to be present in up to 20% of the general population (2). According to one model, there are five types of affective temperaments– Depressive, Hyperthymic, Cyclothymic, Anxious, and Irritable. In both research and clinical settings, the presence of one of more of these affective temperaments can be established by administration of the TEMPS-A questionnaire (Temperament Scale of Memphis, Pisa, Paris and San Diego)(3).
The relationship between affective temperaments and affective illness appears to be complex, with some researchers indicating that affective temperaments represent a “latent stage” of illness (2) while others place affective temperaments on one end of a “spectrum” that leads to more severe forms of illness (4). I will now consider three studies which together help to elucidate the relationship between affective temperaments and affective illness.
In 1992, researchers at the University of Pisa and University of Tennessee analyzed data from 538 patients presenting with a major depressive episode. Unexpectedly, they found that patients with unipolar depression superimposed on hyperthymic temperament presented a unique subcategory (UP-HT). Hyperthymic temperament is described as trait exuberance, cheerfulness, talkativeness and extraversion (5). The UP-HT subgroup had some features comparable to unipolar depression (such as age of onset, presence of melancholia) but others more similar to patients with bipolar disorder (such as equal male/female sex ratio, higher rate of first degree relatives with bipolar disorder). These findings supported the “validity of using hyperthymia as a temperamental indicator of bipolarity in patients suffering from (major depressive episode)” (5).
The 1992 paper is important because it established that the course of affective illness, in this case depression, could be modified by underlying affective temperament. This UP-HT variant, which has genetic similarities to bipolar disorder (similar sex distribution and family history) starts to look more like it should be on a spectrum of bipolar disorder; indeed, in later papers Akiskal referred to UP-HT as “Bipolar Type IV” (4). In this case, consideration of one’s underlying hyperthymic affective temperament in the setting of depression would be helpful in guiding the clinician towards appropriate treatment (i.e. monitoring for antidepressant-induced hypomania, considering mood stabilizer treatment earlier).
In 2003, Akiskal, Hantouche and Allilaire published a study focusing on bipolar II disorder, with (n=74) and without (n=120) cyclothymic temperament (CT) (6). Cyclothymic temperament has been described as a combination of biphasic, abrupt mood swings along with at least four of the following: alternations between lethargy and eutonia, low self-confidence and overconfidence, decreased verbal output and talkativeness, mental confusion and sharpened/creative thinking, tearfulness and jocularity, and introverted self-absorption and uninhibited people-seeking (4). The group found that patients with bipolar II disorder with CT had a younger age of onset of illness, more episodes of depression and delayed recognition/diagnosis of bipolar disorder. Most significantly, the cyclothymic bipolar II group scored significantly higher on “irritable risk taking” than “classic driven-euphoric” items of hypomania. This led to the establishment of “Bipolar II 1/2” (Bipolar II with cyclothymic temperament) – a more “unstable” and “dark” variant of bipolar II disorder (6). Early recognition of “dark” bipolar II disorder is key in order to closely monitor the individual, as the combination of irritability, depression, and impulsivity can have dangerous consequences.
While the above two studies represent some of the best and most interesting work in the field of affective temperaments, questions remain. Specifically, larger studies have been lacking that compare the frequency of particular affective temperaments in clinical and non-clinical populations. More recently, however, a meta-analysis of 26 studies has been published comparing TEMPS scores across mood disorder patients, their first-degree relatives, healthy controls, and other psychiatric disorders (7).
The researchers found that patients with bipolar disorder (BD) had significantly higher cyclothymic (P<0.001), hyperthymic (P<0.001) and irritable (P<0.001) TEMPS scores compared to patients with major depressive disorder (MDD). Depressive and anxious TEMPS scores were not different between the two groups. When comparing bipolar disorder type I (BP-I) with bipolar disorder type II (BP-II) patients, depressive TEMPS scores were lower in BP-I compared with BP-II (P=0.002). This latter finding could lend validity to the clinical observation that BP-II patients spend much more time in a depressive state than in a hypomanic one. In comparing bipolar disorder (BD) to healthy controls (HC), bipolar patients had significantly higher TEMPS scores for cyclothymic, depressive, irritable, and anxious temperaments (P<0.001) with hyperthymic TEMPS scores being higher in the HC group than BD group (P<0.001). Findings were similar when comparing MDD to HC, indicating that having hyperthymic temperament is likely a protective factor for both unipolar and bipolar disorders.
Comparisons of TEMPS scores for bipolar patients in comparison with first-degree BD relatives and healthy controls (HC) are of interest as well. Cyclothymic (P<0.001), irritable (P=0.001) and anxious (P=0.03)TEMPS scores were significantly higher in the BD group compared with BD relatives. In comparing first-degree BD relatives with HC, cyclothymic (P=0.007), irritable (P<0.001) and anxious (P=0.01)TEMPS scores were significantly higher in BD relatives than in HCs.
The results of the meta-analysis help to validate the idea of mood disorders as being on a continuum, with TEMPS scores for cyclothymic and irritable temperaments increasing from healthy controls (HC) through major depressive disorder (MDD) to bipolar disorder (BD). TEMPS scores for hyperthymic temperament increased from MDD through BD to HC. For cyclothymic, irritable and anxious temperaments, TEMPS scores increased from HC through BD relatives to BD (7).
To summarize, data from the past two decades indicate that affective temperaments and mood disorders are closely linked. Akiskal et. al. used their findings to establish the “soft bipolar spectrum”(4) model of illness, which incorporates underlying cyclothymic temperament in combination with recurrent depressive illness. Cyclothymic temperament was found to be a risk factor for the development of bipolar disorder as well as a complicating factor. Cyclothymic temperament in combination with bipolar II portends a “dark” variant of hypomania characterized by irritability impulsivity and high-risk behavior. More recently, a meta-analysis has reinforced the associations between affective temperaments, unipolar vs. bipolar disorder, first-degree relatives and healthy controls. Important questions do remain about the precise nature of these associations. For example, what is the % risk that a patient with a given affective temperament will develop bipolar disorder, and by what process? Only longitudinal, prospective studies following individuals with affective temperaments could begin to answer this question. The complex interactions between the “trait” characteristics of affective temperaments and “state” mood disorders are fascinating and have important implications for both diagnosis and treatment.
Susan Stern, M.D.