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Ethnic differences in allopregnanolone concentrations in
women during rest and following mental stress
SUSAN S. GIRDLER,
a,b
M. BETH MECHLIN,
b
KATHLEEN C. LIGHT,
a,b
and
A. LESLIE MORROW
a
a
Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
b
Department of Psychology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
Abstract
The neuroactive steroid allopregnanolone (ALLO) is stress sensitive, negatively modulates the HPA axis, and has been
implicated in mood disorders. We examined ethnic differences in plasma ALLO at rest and following mental stress in
African American (AA) men (n521) and women (n524) and non-Hispanic White men (n524) and women (n525).
Overall, AA women had lower ALLO concentrations than non-Hispanic White women (po.05), especially following
mental stress ( po.01). Only 20% of AA women showed the expected stress-induced increase in ALLO compared with
59% of non-Hispanic White women ( po.01). No ethnic differences were seen in men. For both ethnic groups,
poststress ALLO was negatively correlated with poststress cortisol ( po.05). Results are interpreted to reflect dys-
regulation in ALLO mechanisms in AA women and may have implications for ethnic differences in mood disorders.
Descriptors: Allopregnanolone, Stress, Ethnic differences
It is well established that relative to Caucasians, African Amer-
icans bear a disproportionate burden of medical illness in the
United States, such as hypertension (Centers for Disease Control
and Prevention, 2005; Flack et al., 2003) and pain-related dis-
orders (Edwards, Doleys, Fillingim, & Lowery, 2001; Edwards,
Fillingim, & Keefe, 2001; McCracken, Matthews, Tang, & Cub,
2001; Riley et al., 2002). Evidence also suggests that African
Americans may have a higher prevalence of specific types of
mental illness, including depression (Bolden & Wicks, 2005; U.S.
Department of Health and Human Services, 1999; Wells, Klap,
Koike, & Sherbourne, 2001). Greater psychosocial stress asso-
ciated with poverty, crime, and racism has been implicated in the
greater rates of both medical and mental illness in African Amer-
ican populations (Anderson, McNeilly, & Myers, 1992; Mechlin,
Maixner, Light, Fisher, & Girdler, 2005; Riolo, Nguyen, Greden,
& King, 2005; Sachs-Ericsson, Plant, & Blazer, 2005). Conse-
quently, numerous studies have examined ethnic differences in
biological responses to stress as a potential pathophysiological
mechanism contributing to the greater rates of illness in African
Americans (e.g. Anderson et al., 1992; Light et al., 1993; Mechlin
et al., 2005; Stoney, Hughes, Kuntz, West, & Thornton, 2002) .
The present report examined ethnic differences in a relatively
novel stress-responsive factor, allopregnanolone (3a-hydroxy-
5a-pregnan-20-one). Allopregnanolone (ALLO) is an A-ring-
reduced metabolite of progesterone (Paul & Purdy, 1992). Pro-
geseterone metabolites fall within the general class of endogenous
steroids termed ‘‘neuroactive steroids,’’ which are pregnane and
androstane steroids that are produced both de novo in brain but
also peripherally in ovary and adrenals. Owing to its lipophili-
city, even peripherally produced ALLO readily crosses the blood
brain barrier, where it rapidly alters central nervous system
(CNS) excitability, producing behavioral effects within seconds
to minutes (Paul & Purdy, 1992; Purdy, Morrow, Moore, &
Paul, 1991). ALLO enhances neuronal inhibition via a potent
and selective interaction with the GABA
A
receptors (nanomolar
concentrations), and it is through this mechanism that it exerts
anxiolytic, analgesic, and anticonvulsant actions, and, at higher
doses, it is sedative, hypnotic, and induces anesthesia (Belelli et
al., 2006; Morrow, Suzdak, & Paul, 1987).
ALLO has been shown to be stress sensitive in rat models,
with CNS levels rising quickly following acute stress (Barbaccia
et al., 1996; Purdy et al., 1991). Peripheral levels in rat also in-
crease significantly following stress, though the response is more
delayed (Paul & Purdy, 1992). Animal models indicate that
stress-induced increases in ALLO serve to negatively modulate
hypothalamic-pituitary-adrenal (HPA) axis activity, thereby
facilitating the recovery of physiologic homeostasis in this sys-
tem following stressful stimuli (Guo et al., 1995; Patchev, Has-
san, Holsboer, & Almeida, 1996). In humans, an early study by
Genazzani et al. (1998) employed endocrine challenge paradigms
in healthy men and women and found that both GnRH and
CRH administration increased serum ALLO levels whereas sup-
pression of adrenal steroidogenesis markedly reduced ALLO.
This research was supported by NIH grants RO1-DA13705 and
GCRC RR00046.
Address reprint requests to: Susan S. Girdler, Ph.D., University of
North Carolina, CB #7175, Medical Research Bldg. A, Mason Farm
Road, Chapel Hill, NC 27599-7175, USA. E-mail: susan_girdler@med.
unc.edu.
Psychophysiology, 43 (2006), 331–336. Blackwell Publishing Inc. Printed in the USA.
Copyright r2006 Society for Psychophysiological Research
DOI: 10.1111/j.1469-8986.2006.00410.x
331
These results suggested that, in humans, both the ovary and
adrenal cortex are major sources of circulating ALLO and that
ALLO is stress responsive.
Although ALLO appears to serve an adaptive function during
the defense reaction, dysregulation of ALLO mechanisms has
been implicated in a number of psychiatric conditions, particularly
mood disorders (Strous, Maayan, & Weizman, 2006). For exam-
ple, in both men and women, patients with current depression
have reduced ALLO concentrations that correlate with severity of
depressive symptoms (Nappi et al., 2001; Romeo et al., 1998;
Strohle et al., 1999, 2000; Uzunova et al., 1998), and clinically
efficacious treatment with selective serotonin re-uptake inhibitors
is associated with increases in ALLO in depressed patients (Strohle
et al., 1999, 2000; Uzunova et al., 1998). The antidepressant-
like effect of ALLO is also well recognized in animal models
(Uzunova, Ceci, Kohler, Uzunov, & Wrynn, 2003; Uzunova et
al., 2004). Moreover, we recently reported that relative to never
depressed women, women with a history of depressive disorders
showed dysregulation in ALLO responses to experimental chal-
lenges (Klatzkin, Morrow, Light, Pedersen, & Girdler, 2006).
Alteration in ALLO mechanisms has also been implicated in
gynecological conditions in women. The postpartum period is char-
acterized by an increased vulnerability to the development of mood
disorders. Progesterone levels rise during pregnancy, followed by a
rapid drop in serum and brain following delivery (Concas et al.,
1998; Luisi et al., 2000), and it is the rapid withdrawal of proges-
terone that has been implicated as a candidate in the induction of
postpartum mood changes (Nappi et al., 2001). However, because
ALLO concentrations increase in parallel with progesterone during
gestation and parturition (Luisi et al., 2000), rapid reductions in
ALLO in the postpartum period may also be a contributing factor
to postpartum dysphoria in vulnerable women. In support of this is
evidence that women with postpartum ‘‘blues’’ have lower circulat-
ing ALLO than euthymic postpartum controls (Nappi et al., 2001).
Thus, although lower ALLO concentrations are associated with
dysphoric mood in both men and women, ALLO may have par-
ticular relevance for mood disturbance in women.
Because African Americans may be at increased risk for
mood disorders (Bolden & Wicks, 2005; U.S. Department of
Health and Human Services, 1999; Wells et al., 2001) and a
recent study documented that, even after controlling for demo-
graphic factors, history of depression, and other predictors, Af-
rican American women were more than twice as likely to
experience postpartum depressive symptoms than non-Hispanic
White women (Howell, Mora, Horowitz, & Leventhal, 2005),
studies on ethnic differences in ALLO may serve to elucidate a
pathophysiological mechanism contributing to ethnic disparities
in mental health. Thus, one purpose of the present report was to
compare African Americans with non-Hispanic Whites for dif-
ferences in ALLO concentrations. Moreover, because it is well
established that stress is an independent predictor of depressive
disorders (e.g., Kendler, Kuhn, & Prescott, 2004) and because
animal models clearly indicate an adaptive role of ALLO fol-
lowing exposure to stress (Barbaccia et al., 1996; Purdy et al.,
1991), we examined ethnic differences in ALLO concentrations
at rest and also following mental stress.
Methods
Participants
Participants that comprise the present report represent a large
subsample of the participants tested in a study designed to ex-
amine ethnicity, menstrual cycle, and stress-induced analgesia
(Mechlin et al. 2005). Of the 107 participants tested in the parent
study, we analyzed ALLO in plasma from 84 participants.
The subsample of participants providing ALLO samples was
composed of 41 men and 44 women, aged 18–47 years. Ap-
proximately half (n545) of the participants self-identified as
African American/Black (21 men, 24 women) whereas the others
were selected based on self-identification as non-Hispanic White
(n539; 20 men, 19 women). Because statistical power was not
sufficient to examine other ethnic groups (7% Asian, 7% Indian,
and 5% Hispanic), subjects endorsing other ethnic categories
were dropped from all analyses.
There were no gender or ethnic group differences in age (range
18–47), diastolic blood pressure (DBP; range 50–87 mmHg), or
heart rate (range 50–92 bpm). There were expected ethnic dif-
ferences in body mass index (BMI), because African Americans
had higher BMIs than non-Hispanic Whites (28.9 vs. 25.1;
F[3,82] 57.92, po.01). For the women, there were no differ-
ences between African American and non-Hispanic Whites in
luteal progesterone concentrations (13.5 vs. 15.4 ng/ml, respec-
tively), with all women exhibiting levels consistent with an
ovulatory luteal phase.
All participants were medically healthy, with no more than
mildly elevated blood pressure (o160/90 mmHg) as determined
during an initial screening session. Only 4 participants (2 African
Americans and 2 non-Hispanic Whites) had elevated BP, defined
as SBP 4135 mmHg and/or DBP 485 mmHg. Additionally,
participants were not taking any prescription medication, in-
cluding oral contraceptives, hormonal replacement therapy, or
psychotropics, and none took any over-the-counter medication
on a regular basis (e.g., nonsteroidal anti-inflammatory agents,
antihistamines). All women reported regular menstrual cycles.
Excluded from participating were participants with chronic
pain conditions (e.g., temporomandibular joint disorder, fibro-
myalgia, arthritis) and those with signs of depression or anxiety
based on Hamilton rating scales (47 for depression, 49for
anxiety). The protocol was approved by the institution’s Insti-
tutional Review Board and all participants provided informed,
written consent prior to participating. Participants received $150
compensation.
Procedures
As part of the larger protocol (see Mechlin et al., 2005), women
were tested three times, once during the early follicular, once
during the late follicular, and once during the luteal phase of their
menstrual cycle. Cycle phases were confirmed using serum est-
radiol and progesterone concentrations. Men were also tested
three times, matched for number of days between test sessions.
Because ALLO levels are nondetectable in a substantial propor-
tion of women in their follicular phase (Girdler, Straneva, Light,
Pedersen, & Morrow, 2001), only luteal phase data are included
in the present report. There were no significant differences in the
proportion of African Americans versus non-Hispanic White
women whose luteal phase session was the first test session (9 vs.
7, respectively), second test session (6 vs. 11), or last test session
(10 vs. 6) (w
2(2)
52.70).
For all participants, laboratory testing began between 12 p.m.
and 2 p.m. An intravenous line (i.v.) was established in an arm
vein and, once it was in place, a curtain was drawn to hide the i.v.
and arm and to minimize awareness of blood sampling. Because
one purpose of the overarching research protocol was to examine
stress-induced analgesia (reported in Mechlin et al., 2005),
332 S.S. Girdler et al.
participants were exposed to a series of pain tests, once after the
mental stressor battery (described below) and once after a rest
control period, counterbalancing order of rest versus stress first
within each ethnic and gender group. Thus, for fully half of each
ethnic/gender group, stress testing was the first event experienced
and preceded all pain testing. For the other half, stress testing
followed one series of pain testing, with a 20-min recovery period
imposed between the last pain test and the baseline rest period.
Baseline. Immediately following the i.v. setup, 20 min of qui-
et rest followed. The first 10 min served as recovery from veni-
puncture, and the last 10 min constituted baseline. Blood was
sampled at minute 10 for baseline ALLO and cortisol.
The Trier Social Stress Test (TSST). The TSST is a stress
test that reliably induces large and consistent HPA and cardi-
ovascular responses (Kirschbaum, Pirke, & Hellhammer, 1993).
The TSST involved the following components: (1) pretask in-
structions (5 min); (2) speech preparation period (5 min), during
which time subjects were left alone to prepare their talk; (3) job
speech (5 min), delivered in front of a ‘‘selection committee’’ and
tape recorded; and (4) Paced Auditory Serial Addition Test
(PASAT; Gronwall, 1977) (8.5 min), involving a tape-recorded
presentation of numbers that were serially added. Subjects had
the opportunity to earn up to $10 for each task based upon
performance.
Stress recovery (10 min). Subjects rested quietly alone.
Blood was sampled at the end of this period to capture the de-
layed plasma cortisol response to the TSST (Kirschbaum et al.,
1993) and also for ALLO, because animal models indicate a
delayed plasma ALLO response to stress (Purdy et al., 1991).
Plasma ALLO (3a,5a-THP) was assessed by radioimmuno-
assay (RIA) following extraction and purification by column
chromatography as previously described (Girdler et al., 2001;
Janis, Devaud, Mitsuyama, & Morrow, 1998). The 3a,5a-THP
antiserum has previously been shown to produce minimal cross-
reactivity with other circulating steroids (Janis et al., 1998).
Cross-reactivity with progesterone (o3%) as well as the stereo-
chemical isomers of 3a,5a-THP is minimal (3a,5b-THP 6.6%;
3b,5a-THP 2.8%; 3b,5-THP 0.5%). In contrast, the steroid
3a-hydroxy-4-pregnen-20-one binds to the antibody to a greater
degree than 3a,5a-THP (169% of 3a,5a-THP). It is unknown,
however, whether 3-hydroxy-4-pregnen-20-one exists in human
serum. If the steroid does exist in human serum, then it may
contribute to the measurement of ALLO; however, because both
ALLO and the pregnen-4 compound are equally efficacious
agonists of GABA
A
receptor mediated Cl uptake (Morrow,
Pace, Purdy, & Paul, 1990), they would be expected to produce
similar effects.
Plasma cortisol was determined by RIA using commercial kits
from ICN Pharmaceuticals. The sensitivity of the assay is excel-
lent at 0.07 mg/dl. The specificity of the RIA for cortisol is high,
showing only 0.05%–2.2% cross-reactivity with most similarly
structured compounds.
Data Reduction and Analyses
Our first aim was to examine ethnic differences in the absolute
concentrations of ALLO at baseline and poststress. Because
ALLO concentrations are significantly greater in women than in
men, gender was treated as an independent variable in the anal-
yses. Thus a 2 (Ethnicity) 2 (Gender) 2 (Stress: baseline vs.
poststress) repeated measures ANOVA was employed with stress
as the repeated factor. Where significant interactions emerged,
these were followed by simple effects analyses to determine the
source of the effect. Post hoc examination of the data revealed
that some individuals exhibited positive changes in ALLO from
baseline to stress, whereas others exhibited negative changes.
Chi-square analysis was used to determine if the percentage of
individuals showing positive versus negative ALLO responses to
stress differed by ethnicity. Finally, we examined the relationship
of plasma ALLO to plasma cortisol concentrations using Pear-
son Product Moment Correlational Analyses.
Results
Gender and Ethnic Differences in ALLO Concentrations at Rest
and Poststress
As expected, women in the luteal phase of their menstrual cycle
had significantly higher levels of ALLO than men at both
baseline rest (1.43 vs. 0.36 ng/ml, respectively) and poststress
time points (1.34 vs. 0.35 ng/ml; main effect of Gender:
F[1,80] 5116.8, po.0001). However, a Gender Ethnicity in-
teraction was also observed, F(1,80) 55.1, po.05. Simple effects
analyses conducted separately in the genders revealed an ethnic
difference in women only (main effect of Ethnicity: F[1,42] 55.8,
po.05) because African American women had lower ALLO
concentrations than non-Hispanic White women at baseline rest
(1.25 vs. 1.62 ng/ml, po.10; d50.52) but especially following
mental stress (1.10 vs. 1.60 ng/ml, po.01; d50.86; Figure 1). In
contrast, there was no difference between African American and
non-Hispanic White men in either baseline ALLO (0.36 vs.
0.35 ng/ml) or poststress ALLO (0.35 vs. 0.35).
The omnibus ANOVA failed to reveal any significant main
effects, F(1.80) 51.72, or interactive effects, Fs(1,80) 50.55–
1.33, involving stress for ALLO concentrations because average
ALLO concentrations did not change significantly from baseline
rest to poststress. Post hoc examination of the data indicated that
the absence of an overall stress effect for ALLO was driven by the
fact that approximately half of the subjects showed an increase in
ALLO whereas the other half showed a decrease in ALLO from
baseline to poststress. Specifically, in the entire sample, a de-
crease in ALLO from baseline to poststress was observed in 57%
of the participants (mean decrease 50.25 ng/ml, SEM 50.04;
d50.74), whereas a mean increase in ALLO was observed in the
other 43% of the participants (mean increase 51
0.16 ng/ml,
Ethnic differences in allopregnanolone 333
1.80
1.64
1.48
1.32
1.16
1.00
Allopregnanolone in ng/mL
Baseline ALLO Post-Stress ALLO
African Americans
(n = 25)
non-Hispanic Whites
(n = 20)
Figure 1. Mean (1SEM) plasma allopregnanolone (ALLO)
concentrations in women at baseline and following mental stress as a
function of ethnic group.
SEM 50.05; d50.50). Paired-comparison ttests revealed that
the average magnitude of the ALLO change was significant
whether negative ( po.0001) or positive ( po.01).
Chi square analyses revealed that African American women
were more likely to exhibit a decrease whereas non-Hispanic
White women were more likely to exhibit an increase in ALLO
levels from baseline to poststress (w
2(1)
57.6, po.01; see Figure
2). In men there were no ethnic differences in the proportion
showing a decrease (50% African American vs. 60% Caucasian/
Others) versus an increase in ALLO (50% African Americans vs.
40% Caucasian/Others; w
2(1)
50.40).
Relationship of ALLO Concentrations to Cortisol Concentrations
Both African Americans and non-Hispanic Whites showed the
expected negative correlation relating poststress ALLO concen-
trations to poststress cortisol (r50.34, po.05 and r50.46,
po.01, respectively). Although the direction of the relationship
was the same for baseline levels, the correlation was statistically
significant only in the non-Hispanic Whites (r50.49, po.01)
but not in the African Americans (r50.23).
Discussion
This is the first study of which we are aware to examine ethnic
differences in ALLO concentrations. We observed that African
American women exhibited both lower resting plasma concen-
trations of ALLO and lower ALLO concentrations following
mental stress. Moreover, African American women were more
likely to show a decrease in ALLO concentrations from rest to
poststress, whereas non-Hispanic White women were more likely
to show an increase. No ethnic differences in ALLO concentra-
tions or in direction of change from rest to poststress were ob-
served in men.
The magnitude and direction of the ALLO response following
stress deserves comment. Although nearly half of the sample
showed a significant increase in ALLO of 10.16 pg/ml from
baseline to poststress, the possibility exists that our sampling
interval did not capture the peak ALLO response to stress and
this could contribute, in part, to the observed ethnic differences in
the proportion of women showing an increase versus decrease in
ALLO poststress. Though no studies exist on the time course of
the ALLO response to stress in humans, our first study on ALLO
reactivity to stress in a primarily Caucasian sample of healthy
women (Girdler et al., 2001) found an average increase in ALLO
of 10.22 pg/ml when ALLO was sampled earlier, at 17 min fol-
lowing the onset of stress. In the present study, we sampled for
poststress ALLO at 30 min following the onset of mental stress
because this time point is associated with peak cortisol responses
(Kirschbaum et al., 1993), but it may not be associated with peak
ALLO responses in humans. This is supported, in part, by our
most recent study on ALLO reactivity to stress (Klatzkin et al.,
2006) that found nonsignificant increases in stress-induced
ALLO in healthy Caucasian women when ALLO was sampled
at 30 and 60 min poststress, even though the 60-min time point
was specifically selected because it is associated with peak serum
ALLO responses to stress in animals (Purdy et al., 1991). Par-
ametric studies in humans designed to sample ALLO at various
time points following a standardized mental stressor battery are
needed. Failure to sample for ALLO when responses to stress
peaked or ethnic differences in the time course of the ALLO
response to stress could have contributed to the ethnic difference
observed in women in the direction of ALLO responses from
baseline to poststress.
Another possibility for the ethnic differences in the directional
change in ALLO may reflect alterations in the regulation of
ALLO in African American women. Consistent with the seminal
paper of Siever and Davis (1985) on the dysregulationhypothesis
of depression, dysregulation in stress-responsive systems is ev-
idenced by more erratic basal output and/or less selectivity in
responsiveness to environmental stimuli. Either of these mech-
anisms could contribute to lower poststress values relative to
baseline values. Similar to the current pattern of results, two
separate studies from our laboratory have documented evidence
for dysregulation in ALLO responses to stress in women with
mood disorders because we found that women with premenstrual
dysphoric disorder or women with histories of depressive disor-
ders exhibit a decrease in ALLO from baseline to poststress not
seen in healthy control women (Girdler et al., 2001; Klatzkin et
al., 2006). It is important to note, however, that while we did not
assess histories of depressive disorders in the present study, none
of the women had current depression or anxiety. Although this is
speculative, given that African American women are at increased
risk to develop mood disorders, particularly postpartum depres-
sion (Howell et al., 2005), the possibility exists that dysregulation
in ALLO mechanisms or responses to stress is a marker for in-
creased vulnerability to mood disorders. Longitudinal studies
would be needed to address this issue.
Irrespective of ethnic differences in the direction of change in
ALLO following stress, the African American women had lower
circulating ALLO levels across both time points relative to the
non-Hispanic White women. Because we did not observe differ-
ences in progesterone concentrations, one possibility is that there
are ethnic differences in the metabolic pathways involved in the
conversion of progesterone to neuroactive steroids. The 5a-re-
ductase enzymes catalyze the reduction of progesterone into
pregnane steroids, which are further reduced to the neuroactive
steroids ALLO or 3a,5a-tetrahydrodeoxycorticosterone (3a,5a-
THDOC). Studies in depressed patients suggest a differential
conversion of progesterone to 3a,5a-THDOC because depressed
patients have lower circulating plasma ALLO but higher plasma
concentrations of 3a,5a-THDOC (Strohle et al., 1999, 2000).
Though both ofthese neuroactive steroids are potent modulators
of the GABA
A
receptors (Purdy, Morrow, Blinn, & Paul, 1990),
it is reasonable to think that shifts in metabolic processes may
have functional significance because distinct neurosteroid
334 S.S. Girdler et al.
100
80
60
40
20
0
% of Each Ethnic Group
Showing Response
Decreased ALLO Increased ALLO
African Americans
(n = 25)
non-Hispanic Whites
(n = 20)
Figure 2. Percent of women showing an increase versus a decrease in
plasma allopregnanolone from baseline to poststress as a function of
ethnic group.
binding sites have different affinities for various neuroactive
steroids (Morrow et al., 1990). Studies designed to assess each of
the neurosteroid metabolites of progesterone will be needed to
clarify whether ethnic differences in the metabolism of proges-
terone to ALLO contribute to lower circulating ALLO concen-
trations in African American women.
Regardless of mechanism, the lower absolute concentration
of ALLO seen in African American women relative to non-
Hispanic White women at both baseline rest and following stress
may have implications for ethnic differences in the development
of stress-related illness. Consistentwith animalmodels, we found
that greater poststress ALLO concentrations were correlated
with lower poststress cortisol concentrations in both the African
Americans and the non-Hispanic Whites. Thus, to the extent that
lower ALLO concentrations, especially following stress, are as-
sociated with diminished capacity to negatively modulate the
HPA axis and facilitate its recovery following stress exposure
(Guo et al., 1995; Patchev et al. 1996), then ethnic differences in
the regulation of the HPA axis by ALLO may contribute to
ethnic differences in the etiology of mood disorders.
In conclusion, the results of this study suggest that African
American women have lower circulating concentrations of
ALLO and may also exhibit dysregulation in ALLO responsive-
ness to stress. Future studies on the time course of the ALLO
stress response in humans are needed to clarify the nature of the
ethnic differences in the poststress ALLO measure. Evidence for
an association of lower poststress ALLO with higher poststress
cortisol suggests there may be ethnic differences in the regulation
of the HPA axis by ALLO following stress. It is unclear why no
ethnic differences in men were observed in the present study,
though generally lower concentrations in men may have pre-
vented us from detecting ethnic differences. For women, how-
ever, ALLO may have special relevance for ethnic differences in
mood disorders, particularly postpartum depression.
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(Receiv ed March 9, 2006; Accepted May 1, 2006)
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