Mindfulness meditation as a therapeutic intervention has been shown to have positive effects on psychological problems such as depression, pain or anxiety disorders. In this study, we used functional near-infrared spectroscopy (fNIRS) to detect differences in hemodynamic responses of meditation experts (14 participants) and a control group (16 participants) in a resting and a mindfulness condition. In both conditions, the sound of a meditation bowl was used to find group differences in the auditory system and adjacent cortical areas. Different lateralization patterns of the brain were found in expert meditators while being in a resting state (amplified left hemisphere) or being in mindfulness state (amplified right hemisphere). Compared to the control group, meditation experts had a more widespread pattern of activation in the auditory cortex, while resting. In the mindfulness condition, the control group showed a decrease of activation in higher auditory areas (BA 1, 6 and 40), whereas the meditation experts had a significant increase in those areas. In addition, meditation expert had highly activated brain areas (BA 39, 40, 44 and 45) beyond the meditative task itself, indicating possible long-term changes in the brain and their positive effects on empathy, meta cognitive skills and health.

OBJECTIVES:The purpose of this study was to conduct the first randomized controlled trial (RCT) to evaluate the effectiveness of a second-generation mindfulness-based intervention (SG-MBI) for treating fibromyalgia syndrome (FMS). Compared to first-generation mindfulness-based interventions, SG-MBIs are more acknowledging of the spiritual aspect of mindfulness.

DESIGN:A RCT employing intent-to-treat analysis.

METHODS:Adults with FMS received an 8-week SG-MBI known as meditation awareness training (MAT; n = 74) or an active control intervention known as cognitive behaviour theory for groups (n = 74). Assessments were performed at pre-, post-, and 6-month follow-up phases.

RESULTS:Meditation awareness training participants demonstrated significant and sustained improvements over control group participants in FMS symptomatology, pain perception, sleep quality, psychological distress, non-attachment (to self, symptoms, and environment), and civic engagement. A mediation analysis found that (1) civic engagement partially mediated treatment effects for all outcome variables, (2) non-attachment partially mediated treatment effects for psychological distress and sleep quality, and (3) non-attachment almost fully mediated treatment effects for FMS symptomatology and pain perception. Average daily time spent in meditation was found to be a significant predictor of changes in all outcome variables.

CONCLUSIONS:Meditation awareness training may be a suitable treatment for adults with FMS and appears to ameliorate FMS symptomatology and pain perception by reducing attachment to self. Statement of contribution What is already known on this subject? Designing interventions to treat fibromyalgia syndrome (FMS) continues to be a challenge. There is growing interest into the applications of mindfulness-based interventions for treating FMS. Second-generation mindfulness-based interventions (SG-MBIs) are a key new direction in mindfulness research. What does this study add? Meditation awareness training - an SG-MBI - resulted in significant reductions in FMS symptomatology. SG-MBIs recognize the spiritual aspect of mindfulness and may have a role in the treatment of FMS.

Coronary heart disease is the major cause of global cardiovascular mortality and morbidity. Lifestyle behaviour contributes as a risk factor: unhealthy diet, sedentary lifestyle, tobacco, alcohol, hypertension, diabetes, dyslipidemia and psychosocial stress. Atherosclerosis pathologic mechanisms involving oxidative stress, dyslipidemia, inflammation and senescence are associated with arterial wall damage and plaque formation. Stress reduction was observed in several types of meditation. After meditation, hormonal orchestration modulates effects in the central nervous system and in the body. All types of meditation are associated with blood pressure control, enhancement in insulin resistance, reduction of lipid peroxidation and cellular senescence, independent of type of meditation. This review presents scientific evidence to explain how meditation can produce beneficial effects on the cardiovascular system, and particularly regarding vascular aspects.

OBJECTIVE:To conduct a comprehensive review and meta-analysis of the effectiveness of meditation on a variety of asthma outcomes.

METHODS:We searched MEDLINE, EMBASE, CINAHL, PsycINFO and AMED in June 2016 to identify randomised controlled trials (RCTs) investigating the effectiveness of meditation in adults with asthma. No restriction was put on language or year of publication. Study quality was assessed using The Cochrane Risk of Bias Assessment Tool. Meta-analysis was carried out using RevMan 5.3.

RESULTS:Four RCTS involving 201 patients met the inclusion criteria. Quality of studies was inconsistent with only one study reporting adequate allocation concealment. Disease-specific quality of life was assessed in two trials; a pooled result involving 62 intervention and 65 control participants indicated a significant improvement in quality of life in the meditation group compared to the control group (SMD 0.40, 95% CI 0.05 to 0.76). A pooled result from all four studies indicated the uncertain effect of meditation in forced expiratory volume in one second (FEV1) (SMD -0.67, 95% CI -2.17 to 0.82). Results from the individual trials suggest that meditation may be helpful in reducing perceived stress and the use of short-term rescue medication.

CONCLUSION:Our review suggests that there is some evidence that meditation is beneficial in improving quality of life in asthma patients. As two out of four studies in our review were of poor quality, further trials with better methodological quality are needed to support or refute this finding.

OBJECTIVE:Our objective was to assess the safety, feasibility, and effects of the standardized 8-week mindfulness-based stress reduction (MBSR) course in adults with migraines.

BACKGROUND:Stress is a well-known trigger for headaches. Research supports the general benefits of mind/body interventions for migraines, but there are few rigorous studies supporting the use of specific standardized interventions. MBSR is a standardized 8-week mind/body intervention that teaches mindfulness meditation/yoga. Preliminary research has shown MBSR to be effective for chronic pain syndromes, but it has not been evaluated for migraines.

METHODS:We conducted a randomized controlled trial with 19 episodic migraineurs randomized to either MBSR (n = 10) or usual care (n = 9). Our primary outcome was change in migraine frequency from baseline to initial follow-up. Secondary outcomes included change in headache severity, duration, self-efficacy, perceived stress, migraine-related disability/impact, anxiety, depression, mindfulness, and quality of life from baseline to initial follow-up.

RESULTS:MBSR was safe (no adverse events), with 0% dropout and excellent adherence (daily meditation average: 34 ± 11 minutes, range 16-50 minutes/day). Median class attendance from 9 classes (including retreat day) was 8 (range [3, 9]); average class attendance was 6.7 ± 2.5. MBSR participants had 1.4 fewer migraines/month (MBSR: 3.5 to 1.0 vs control: 1.2 to 0 migraines/month, 95% confidence intervalCI [-4.6, 1.8], P = .38), an effect that did not reach statistical significance in this pilot sample. Headaches were less severe, although not significantly so (-1.3 points/headache on 0-10 scale, [-2.3, 0.09], P = .053) and shorter (-2.9 hours/headache, [-4.6, -0.02], P = .043) vs control. MigraineDisability Assessment and Headache Impact Test-6 dropped in MBSR vs control (-12.6, [-22.0, -1.0], P = .017 and -4.8, [-11.0, -1.0], P = .043, respectively). Self-efficacy and mindfulness improved in MBSR vs control (13.2 [1.0, 30.0], P = .035 and 13.1 [3.0, 26.0], P = .035 respectively).

CONCLUSIONS:MBSR is safe and feasible for adults with migraines. Although the small sample size of this pilot trial did not provide power to detect statistically significant changes in migraine frequency or severity, secondary outcomes demonstrated this intervention had a beneficial effect on headache duration, disability, self-efficacy, and mindfulness. Future studies with larger sample sizes are warranted to further evaluate this intervention for adults with migraines. This study was prospectively registered (ClinicalTrials.gov identifier NCT01545466).

OBJECTIVE:Our objective was to assess the safety, feasibility, and effects of the standardized 8-week mindfulness-based stress reduction (MBSR) course in adults with migraines.

BACKGROUND:Stress is a well-known trigger for headaches. Research supports the general benefits of mind/body interventions for migraines, but there are few rigorous studies supporting the use of specific standardized interventions. MBSR is a standardized 8-week mind/body intervention that teaches mindfulness meditation/yoga. Preliminary research has shown MBSR to be effective for chronic pain syndromes, but it has not been evaluated for migraines.

METHODS:We conducted a randomized controlled trial with 19 episodic migraineurs randomized to either MBSR (n = 10) or usual care (n = 9). Our primary outcome was change in migraine frequency from baseline to initial follow-up. Secondary outcomes included change in headache severity, duration, self-efficacy, perceived stress, migraine-related disability/impact, anxiety, depression, mindfulness, and quality of life from baseline to initial follow-up.

RESULTS:MBSR was safe (no adverse events), with 0% dropout and excellent adherence (daily meditation average: 34 ± 11 minutes, range 16-50 minutes/day). Median class attendance from 9 classes (including retreat day) was 8 (range [3, 9]); average class attendance was 6.7 ± 2.5. MBSR participants had 1.4 fewer migraines/month (MBSR: 3.5 to 1.0 vs control: 1.2 to 0 migraines/month, 95% confidence intervalCI [-4.6, 1.8], P = .38), an effect that did not reach statistical significance in this pilot sample. Headaches were less severe, although not significantly so (-1.3 points/headache on 0-10 scale, [-2.3, 0.09], P = .053) and shorter (-2.9 hours/headache, [-4.6, -0.02], P = .043) vs control. MigraineDisability Assessment and Headache Impact Test-6 dropped in MBSR vs control (-12.6, [-22.0, -1.0], P = .017 and -4.8, [-11.0, -1.0], P = .043, respectively). Self-efficacy and mindfulness improved in MBSR vs control (13.2 [1.0, 30.0], P = .035 and 13.1 [3.0, 26.0], P = .035 respectively).

CONCLUSIONS:MBSR is safe and feasible for adults with migraines. Although the small sample size of this pilot trial did not provide power to detect statistically significant changes in migraine frequency or severity, secondary outcomes demonstrated this intervention had a beneficial effect on headache duration, disability, self-efficacy, and mindfulness. Future studies with larger sample sizes are warranted to further evaluate this intervention for adults with migraines. This study was prospectively registered (ClinicalTrials.gov identifier NCT01545466).

We conducted a systematic review and meta-analysis that synthesized evidence from randomized controlled trials of meditation interventions to provide estimates of their efficacy and safety in treating adults diagnosed with posttraumatic stress disorder (PTSD). This review was based on an established protocol (PROSPERO: CRD42015025782) and is reported according to PRISMA guidelines. Outcomes of interest included PTSD symptoms, depression, anxiety, health-related quality of life, functional status, and adverse events. Meta-analyses were conducted using the Hartung-Knapp-Sidik-Jonkman method for random-effects models. Quality of evidence was assessed using the Grade of Recommendations Assessment, Development, and Evaluation (GRADE) approach. In total, 10 trials on meditation interventions for PTSD with 643 participants met inclusion criteria. Across interventions, adjunctive meditation interventions of mindfulness-based stress reduction, yoga, and the mantram repetition program improve PTSD and depression symptoms compared with control groups, but the findings are based on low and moderate quality of evidence. Effects were positive but not statistically significant for quality of life and anxiety, and no studies addressed functional status. The variety of meditation intervention types, the short follow-up times, and the quality of studies limited analyses. No adverse events were reported in the included studies; only half of the studies reported on safety. Meditation appears to be effective for PTSD and depression symptoms, but in order to increase confidence in findings, more high-quality studies are needed on meditation as adjunctive treatment with PTSD-diagnosed participant samples large enough to detect statistical differences in outcomes. (PsycINFO Database Record

We conducted a systematic review and meta-analysis that synthesized evidence from randomized controlled trials of meditation interventions to provide estimates of their efficacy and safety in treating adults diagnosed with posttraumatic stress disorder (PTSD). This review was based on an established protocol (PROSPERO: CRD42015025782) and is reported according to PRISMA guidelines. Outcomes of interest included PTSD symptoms, depression, anxiety, health-related quality of life, functional status, and adverse events. Meta-analyses were conducted using the Hartung-Knapp-Sidik-Jonkman method for random-effects models. Quality of evidence was assessed using the Grade of Recommendations Assessment, Development, and Evaluation (GRADE) approach. In total, 10 trials on meditation interventions for PTSD with 643 participants met inclusion criteria. Across interventions, adjunctive meditation interventions of mindfulness-based stress reduction, yoga, and the mantram repetition program improve PTSD and depression symptoms compared with control groups, but the findings are based on low and moderate quality of evidence. Effects were positive but not statistically significant for quality of life and anxiety, and no studies addressed functional status. The variety of meditation intervention types, the short follow-up times, and the quality of studies limited analyses. No adverse events were reported in the included studies; only half of the studies reported on safety. Meditation appears to be effective for PTSD and depression symptoms, but in order to increase confidence in findings, more high-quality studies are needed on meditation as adjunctive treatment with PTSD-diagnosed participant samples large enough to detect statistical differences in outcomes. (PsycINFO Database Record

OBJECTIVE:Interest in meditation to manage posttraumatic stress disorder (PTSD) symptoms is increasing. Few studies have examined the effectiveness of meditation programs offered to Veterans within Department of Veterans Affairs (VA) mental health services. The current study addresses this gap using data from a multisite VA demonstration project.

METHOD:Evaluation data collected at 6 VA sites (N = 391 Veterans) before and after a meditation program, and a treatment-as-usual (TAU) program, were examined here using random effects meta-analyses. Site-specific and aggregate between group effect sizes comparing meditation programs to TAU were determined for PTSD severity measured by clinical interview and self-report. Additional outcomes included experiential avoidance and mindfulness.

RESULTS:In aggregate, analyses showed medium effect sizes for meditation programs compared to TAU for PTSD severity (clinical interview: effect size (ES) = -0.32; self-report: ES = -0.39). Similarly sized effects of meditation programs were found for overall mindfulness (ES = 0.41) and 1 specific aspect of mindfulness, nonreactivity to inner experience (ES = .37). Additional findings suggested meditation type and program completion differences each moderated program effects.

CONCLUSIONS:VA-sponsored meditation programs show promise for reducing PTSD severity in Veterans receiving mental health services. Where meditation training fits within mental health services, and for whom programs will be of interest and effective, require further clarification. (PsycINFO Database Record

OBJECTIVE: We tested whether meditation can reduce sympathetic activation, evaluated by norepinephrine blood levels (NE), and improve quality of life in elderly persons with congestive heart failure (CHF). DESIGN AND SETTING: This was a prospective, randomized study conducted from April 2000 to October 2001 in an ambulatory care teaching hospital in São Paulo, Brazil. SUBJECTS: We studied 19 patients with CHF, 74.8 +/- 6.7 years old, receiving diuretics, optimal doses of an angiotensin-converting enzyme inhibitor or angiotensin II inhibitor, maximum tolerated carvedilol dose (23.1 +/- 13.6 mg) and spironolactone 25 mg (10 patients). INTERVENTIONS: After 2 months of optimal treatment with carvedilol, patients were randomized into two groups. The meditation group (M) was provided an audiotape, 30 minutes long, to listen to at home, twice a day, for 12 weeks, plus a weekly meeting. The control group (C) just had weekly meetings. MAIN OUTCOME MEASURES: We determined before and after 14 +/- k1 weeks, NE (in pg/mL); quality of life with the Minnesota Living with Heart Failure Questionnaire (MLWHFQ); VO2 and VE/VCO2 slope by cardiopulmonary exercise testing; left ventricular ejection fraction (LVEF), and left ventricular end-diastolic volume index (LVDDi) measured by echocardiography. RESULTS: Meditation reduced NE (mean +/- SEM) from 677.7 +/- 96.6 to 387.1 +/- 39.1 pg/mL (p = 0.008) in M versus 491.4 +/- 35.9 to 470.6 +/- 31.2 (p = 0.34) in C; improved MLWHFQ total score (mean +/- SEM) from 33.2 +/- 6.6 to 21.6 +/- 6.8 points (p = 0.02) in M versus 18.4 +/- 8.0 to 25.1 +/- 8.9 (p = 0.41) in C; and reduced the VE/VCO2 slope (mean +/- SEM) from 31.2 +/- 3.0 to 28.2 +/- 2.6 (p = 0.04) in M versus 28.4 +/- 2.7 to 28.8 +/- 2.6 (p = 0.24) in C. No changes occurred in LVEF, LVDDi, and VO(2). CONCLUSIONS: In elderly patients with optimally treated CHF, meditation reduced NE, improved quality of life, and reduced the VE/VCO(2) slope. Our results support the possible role of meditation as a new hope in the treatment of CHF.

BACKGROUND AND PURPOSE:Studies investigating psychological interventions for the promotion of well-being in people with amyotrophic lateral sclerosis (ALS) are lacking. The purpose of the current study was to examine the use of an ALS-specific mindfulness-based intervention for improving quality of life in this population.

METHODS:A randomized, open-label and controlled clinical trial was conducted on the efficacy of an ALS-specific meditation programme in promoting quality of life. Adults who received a diagnosis of ALS within 18 months were randomly assigned either to usual care or to an 8-week meditation training based on the original mindfulness-based stress reduction programme and tailored for people with ALS. Quality of life, assessed with the ALS-Specific Quality of Life Revised scale, represented the primary outcome, whilst secondary outcomes included anxiety and depression, assessed with the Hospital Anxiety and Depression Scale, and specific quality of life domains. Participants were assessed at recruitment and after 2, 6 and 12 months. The efficacy of the treatment was assessed on an intention-to-treat basis of a linear mixed model.

RESULTS:A hundred participants were recruited between November 2012 and December 2014. Over time, there was a significant difference between the two groups in terms of quality of life (β = 0.24, P = 0.015, d = 0.89). Significant differences between groups over time were also found for anxiety, depression, negative emotions, and interaction with people and the environment.

CONCLUSIONS:An ALS-specific meditation programme is beneficial for the quality of life and psychological well-being of people with ALS.

Recent evidence suggests that the effects of meditation practice on affective processing and resilience have the potential to induce neuroplastic changes within the amygdala. Notably, literature speculates that meditation training may reduce amygdala activity during negative affective processing. Nonetheless, studies have thus far not verified this speculation. In this longitudinal study, participants (N = 21, 9 men) were trained in awareness-based compassion meditation (ABCM) or matched relaxation training. The effects of meditation training on amygdala activity were examined during passive viewing of affective and neutral stimuli in a non-meditative state. We found that the ABCM group exhibitedsignificantly reduced anxiety and right amygdala activity during negative emotion processing than the relaxation group. Furthermore, ABCM participants who performed more compassion practice had stronger right amygdala activity reduction during negative emotion processing. The lower right amygdala activity after ABCM training may be associated with a general reduction in reactivity and distress. As all participants performed the emotion processing task in a non-meditative state, it appears likely that the changes in right amygdala activity are carried over from the meditation practice into thenon-meditative state. These findings suggest that the distress-reducing effects of meditation practice on affective processing may transfer to ordinary states, which have important implications on stress management.

Pediatric inflammatory bowel disease is an autoimmune disease that causes chronic inflammation of the gastrointestinal mucosa. There is emerging evidence that the brain-gut connection affects inflammatory bowel disease (IBD) patients more than previously thought. This is evidenced by comorbid mood disorders, irritable bowel symptoms concurrent with quiescent IBD, and the potential of psychosocial stressors to trigger IBD flares. Mind-body interventions such as psychotherapy, relaxation, mindfulness, biofeedback, yoga, and clinical hypnosis offer an adjunct to standard medical treatment for IBD. We will review the current evidence base for these mind- body interventions in the treatment of pediatric IBD, illustrate a case study, and offer suggestions for future research for this promising field.

The use of mind-body therapies, including Tai Chi, Qigong, yoga, and meditation, has grown steadily in recent years. These approaches have been shown to be effective in reducing symptoms and improving quality of life, and research has begun to examine the impact of these therapies on biological processes, including inflammation. A review of 26 randomized controlled trials was conducted to describe the effects of mind-body therapies (MBTs) on circulating, cellular, and genomic markers of inflammation. This qualitative evaluation showed mixed effects of MBTs on circulating inflammatory markers, including CRP and IL-6, and on measures of stimulated cytokine production. More consistent findings were seen for genomic markers, with trials showing decreased expression of inflammation-related genes and reduced signaling through the proinflammatory transcription factor NF-κB. Potential mechanisms for these effects are discussed, including alterations in neuroendocrine, neural, and psychological and behavioral processes.

Attention-deficit/hyperactivity disorder (ADHD) is pervasive among the pediatric population and new treatments with minimal adverse effects are necessary to be studied. The purpose of this article is to review current research studying mind-body therapies for treatment of children diagnosed with ADHD. Literature was reviewed pertaining to the effectiveness of movement-based therapies and mindfulness/meditation-based therapies for ADHD. Many positive effects of yoga, Tai Chi, physical activity, and meditation may significantly improve symptoms of ADHD among children.

This study investigates the relationship between mindfulness, meditation, cognition and stress in people with Alzheimer's disease (AD), dementia, mild cognitive impairment and subjective cognitive decline. Accordingly, we explore how the use of meditation as a behavioural intervention can reduce stress and enhance cognition, which in turn ameliorates some dementia symptoms. A narrative review of the literature was conducted with any studies using meditation as an intervention for dementia or dementia-related memory conditions meeting inclusion criteria. Studies where moving meditation was the main intervention were excluded due to the possible confounding of exercise. Ten papers were identified and reviewed. There was a broad use of measures across all studies, with cognitive assessment, quality of life and perceived stress being the most common. Three studies used functional magnetic resonance imaging to measure functional changes to brain regions during meditation. The interventions fell into the following three categories: mindfulness, most commonly mindfulness-based stress reduction (six studies); Kirtan Kriya meditation (three studies); and mindfulness-based Alzheimer's stimulation (one study). Three of these studies were randomised controlled trials. All studies reported significant findings or trends towards significance in a broad range of measures, including a reduction of cognitive decline, reduction in perceived stress, increase in quality of life, as well as increases in functional connectivity, percent volume brain change and cerebral blood flow in areas of the cortex. Limitations and directions for future studies on meditation-based treatment for AD and stress management are suggested.

Mind wandering can be costly, especially when we are engaged in attentionally demanding tasks. Preliminary studies suggest that mindfulness can be a promising antidote for mind wandering, albeit the evidence is mixed. To better understand the exact impact of mindfulness on mind wandering, we had a sample of highly anxious undergraduate students complete a sustained-attention task during which off-task thoughts including mind wandering were assessed. Participants were randomly assigned to a meditation or control condition, after which the sustained-attention task was repeated. In general, our results indicate that mindfulness training may only have protective effects on mind wandering for anxious individuals. Meditation prevented the increase of mind wandering over time and ameliorated performance disruption during off-task episodes. In addition, we found that the meditation intervention appeared to promote a switch of attentional focus from the internal to present-moment external world, suggesting important implications for treating worrying in anxious populations.

Chronic migraine (CM) is a disabling condition arising from a complex mixture of interconnected biological, psychological and social factors, and is often associated with medication overuse (MO). Mindfulness is emerging as a helpful treatment for pain, and one study showed that the longitudinal 12 months' course of CM-MO patients that attended mindfulness-based treatment alone was similar to that of patients receiving medical prophylaxis alone; in this study, we describe the course of biomarkers of inflammation. Our results provide initial evidence of sustained similar effects on reduced concentration of biomarkers of inflammation, although not sizeable enough to reach statistical significance. Whether more intensive treatment and/or larger samples would lead to greater changes is unknown, but these encouraging preliminary findings suggest further research is warranted.

Chronic migraine (CM) is a disabling condition arising from a complex mixture of interconnected biological, psychological and social factors, and is often associated with medication overuse (MO). Mindfulness is emerging as a helpful treatment for pain, and one study showed that the longitudinal 12 months' course of CM-MO patients that attended mindfulness-based treatment alone was similar to that of patients receiving medical prophylaxis alone; in this study, we describe the course of biomarkers of inflammation. Our results provide initial evidence of sustained similar effects on reduced concentration of biomarkers of inflammation, although not sizeable enough to reach statistical significance. Whether more intensive treatment and/or larger samples would lead to greater changes is unknown, but these encouraging preliminary findings suggest further research is warranted.

Meditation is a popular form of stress management, argued to mediate stress reactivity. However, many studies in this field commonly fail to include an active control group. Given the frequency with which people are selecting meditation as a form of self-management, it is important to validate if the practice is effective in mediating stress-reactivity using well-controlled studies. Thus, we aimed to conduct a meta-analysis investigating the neurobiological effects of meditation, including focused attention, open monitoring and automatic self-transcending subtypes, compared to an active control, on markers of stress. In the current meta-analysis and systematic review, we included randomised controlled trials comparing meditation interventions compared to an active control on physiological markers of stress. Studied outcomes include cortisol, blood pressure, heart-rate, lipids and peripheral cytokine expression. Forty-five studies were included. All meditation subtypes reduced systolic blood pressure. Focused attention meditations also reduced cortisol and open monitoring meditations also reduced heart rate. When all meditation forms were analysed together, meditation reduced cortisol, C - reactive protein, blood pressure, heart rate, triglycerides and tumour necrosis factor-alpha. Overall, meditation practice leads to decreased physiological markers of stress in a range of populations.