Variability in human tooth cementum thickness reflecting functional processes.

OBJECTIVE: The aim of this study was to investigate the thickness of acellular extrinsic fibre cementum (AEFC) at four root positions of anterior and posterior teeth with special focus on functional aspects. Furthermore, the correlations between cementum thickness and chronological age and sex are investigated. BACKGROUND: While numerous studies confirm continuous cementum apposition with age, masticatory forces as well as physiological and orthodontically induced tooth movements also have the potential to affect tooth cementum thickness. MATERIALS AND METHODS: Undecalcified teeth were embedded in resin and transverse-sectioned in the cervical third of the root. Two sections per root were selected, and digital images at four positions were obtained (mesial, distal, oral, and vestibular) using light microscopy. The AEFC thickness of 99 teeth (anterior = 66, posterior = 33, male = 54, female = 45) were measured in both sections. The differences in mean values between root positions and the association of root position variation with tooth type, age, sex, and subject as well as the overall effects of age and sex were analysed using a mixed model. RESULTS: First incisors and canines showed the greatest mean AFEC thickness, in contrast to premolars which had the lowest values. Differences were found across the four root positions, with a pattern varying considerably between anterior and posterior teeth and between maxilla and mandible in the anterior teeth. An interaction between root position and subject pointed to the existence of an individual component in the variation of AEFC thickness across the four root positions. There was an age trend with an almost linear increase in cementum thickness of 1 µm per year. Overall, females tended to exhibit a significantly lesser AEFC thickness compared to males. CONCLUSIONS: Distinct differences in the pattern of thickness values across the four root positions in anterior and posterior teeth support the assumption that the AEFC is strongly affected by functional processes. In addition to sex-specific differences and age-related trends, the root position variation of AEFC thickness varies from individual to individual.

Population Genetics and Signatures of Selection in Early Neolithic European Farmers.

Human expansion in the course of the Neolithic transition in western Eurasia has been one of the major topics in ancient DNA research in the last 10 years. Multiple studies have shown that the spread of agriculture and animal husbandry from the Near East across Europe was accompanied by large-scale human expansions. Moreover, changes in subsistence and migration associated with the Neolithic transition have been hypothesized to involve genetic adaptation. Here, we present high quality genome-wide data from the Linear Pottery Culture site Derenburg-Meerenstieg II (DER) (N = 32 individuals) in Central Germany. Population genetic analyses show that the DER individuals carried predominantly Anatolian Neolithic-like ancestry and a very limited degree of local hunter-gatherer admixture, similar to other early European farmers. Increasing the Linear Pottery culture cohort size to ∼100 individuals allowed us to perform various frequency- and haplotype-based analyses to investigate signatures of selection associated with changes following the adoption of the Neolithic lifestyle. In addition, we developed a new method called Admixture-informed Maximum-likelihood Estimation for Selection Scans that allowed us test for selection signatures in an admixture-aware fashion. Focusing on the intersection of results from these selection scans, we identified various loci associated with immune function (JAK1, HLA-DQB1) and metabolism (LMF1, LEPR, SORBS1), as well as skin color (SLC24A5, CD82) and folate synthesis (MTHFR, NBPF3). Our findings shed light on the evolutionary pressures, such as infectious disease and changing diet, that were faced by the early farmers of Western Eurasia.

Massive migration from the steppe was a source for Indo-European languages in Europe.

We generated genome-wide data from 69 Europeans who lived between 8,000-3,000 years ago by enriching ancient DNA libraries for a target set of almost 400,000 polymorphisms. Enrichment of these positions decreases the sequencing required for genome-wide ancient DNA analysis by a median of around 250-fold, allowing us to study an order of magnitude more individuals than previous studies and to obtain new insights about the past. We show that the populations of Western and Far Eastern Europe followed opposite trajectories between 8,000-5,000 years ago. At the beginning of the Neolithic period in Europe, ∼8,000-7,000 years ago, closely related groups of early farmers appeared in Germany, Hungary and Spain, different from indigenous hunter-gatherers, whereas Russia was inhabited by a distinctive population of hunter-gatherers with high affinity to a ∼24,000-year-old Siberian. By ∼6,000-5,000 years ago, farmers throughout much of Europe had more hunter-gatherer ancestry than their predecessors, but in Russia, the Yamnaya steppe herders of this time were descended not only from the preceding eastern European hunter-gatherers, but also from a population of Near Eastern ancestry. Western and Eastern Europe came into contact ∼4,500 years ago, as the Late Neolithic Corded Ware people from Germany traced ∼75% of their ancestry to the Yamnaya, documenting a massive migration into the heartland of Europe from its eastern periphery. This steppe ancestry persisted in all sampled central Europeans until at least ∼3,000 years ago, and is ubiquitous in present-day Europeans. These results provide support for a steppe origin of at least some of the Indo-European languages of Europe.

A distinct section of the Early Bronze Age society? Stable isotope investigations of burials in settlement pits and multiple inhumations of the Únetice culture in central Germany.

OBJECTIVES: Inhumations in so-called settlement pits and multiple interments are subordinate burial practices of the Early Bronze Age Únetice culture in central Germany (2200-1700/1650 BC). The majority of the Únetice population was entombed as single inhumations in rectangular grave pits with a normative position of the body. The goal of the study was to test archaeological hypotheses that the deviant burials may represent socially distinct or nonlocal individuals. MATERIALS AND METHODS: The study comprised up to two teeth and one bone each of 74 human individuals from eight sites and faunal comparative samples. The inhumations included regular, deviant burials in so-called settlement or storage pits, and multiple burials. We investigated radiogenic strontium isotope compositions of tooth enamel ((87) Sr/(86) Sr) and light stable isotope ratios of carbon and nitrogen of bone collagen (δ(13) C, δ(15) N) aiming at the disclosure of residential changes and dietary patterns. RESULTS: Site-specific strontium isotope data ranges mirror different geological properties including calcareous bedrock, loess, and glacial till. Independent from burial types, they disclose low portions of nonlocal individuals of up to some 20% at the individual sites. The light stable isotope ratios of burials in settlement pits and rectangular graves overlap widely and indicate highly similar dietary habits. DISCUSSION: The analytical results let to conclude that inhumations in settlement pits and multiple burials were two of the manifold burial practices of the Early Bronze Age. The selection criteria of the individuals for the different forms of inhumation remained undisclosed.

The Correlation of Tooth Sizes and Jaw Dimensions with Biological Sex and Stature in a Contemporary Central European Population.

Dental anthropology provides a deep insight into biological, ecological and cultural aspects associated with human individuality, behaviour and living conditions and the environment. Our study uses a correlation analysis to test the metric relationships between tooth sizes and jaw dimensions and juxtaposes them with biological sex and stature. A sample of n = 100 dental casts was used to record metric dental data including the mesio-distal and bucco-lingual tooth crown diameters and nine upper and lower jaw dimensions. All crown diameters were highly correlated with both stature and biological sex, with the canines exhibiting the highest correlation. The majority of jaw dimensions exhibited similar correlations. Our results suggest that the differences between the sexes in most crown diameters and some jaw dimensions may be related to the stature of the individuals measured. Two groups of closely correlating features emerged among the jaw dimensions, differing in their degree of correlation with crown diameters and with sex. The results and insights obtained are highly relevant for evolutionary biology, dentistry, craniofacial research, bioarchaeology and forensic odontology.

Socio-cultural practices may have affected sex differences in stature in Early Neolithic Europe.

The rules and structure of human culture impact health as much as genetics or environment. To study these relationships, we combine ancient DNA (n = 230), skeletal metrics (n = 391), palaeopathology (n = 606) and dietary stable isotopes (n = 873) to analyse stature variation in Early Neolithic Europeans from North Central, South Central, Balkan and Mediterranean regions. In North Central Europe, stable isotopes and linear enamel hypoplasias indicate high environmental stress across sexes, but female stature is low, despite polygenic scores identical to males, and suggests that cultural factors preferentially supported male recovery from stress. In Mediterranean populations, sexual dimorphism is reduced, indicating male vulnerability to stress and no strong cultural preference for males. Our analysis indicates that biological effects of sex-specific inequities can be linked to cultural influences at least as early as 7,000 yr ago, and culture, more than environment or genetics, drove height disparities in Early Neolithic Europe.

Ancient DNA from European early neolithic farmers reveals their near eastern affinities.

In Europe, the Neolithic transition (8,000-4,000 B.C.) from hunting and gathering to agricultural communities was one of the most important demographic events since the initial peopling of Europe by anatomically modern humans in the Upper Paleolithic (40,000 B.C.). However, the nature and speed of this transition is a matter of continuing scientific debate in archaeology, anthropology, and human population genetics. To date, inferences about the genetic make up of past populations have mostly been drawn from studies of modern-day Eurasian populations, but increasingly ancient DNA studies offer a direct view of the genetic past. We genetically characterized a population of the earliest farming culture in Central Europe, the Linear Pottery Culture (LBK; 5,500-4,900 calibrated B.C.) and used comprehensive phylogeographic and population genetic analyses to locate its origins within the broader Eurasian region, and to trace potential dispersal routes into Europe. We cloned and sequenced the mitochondrial hypervariable segment I and designed two powerful SNP multiplex PCR systems to generate new mitochondrial and Y-chromosomal data from 21 individuals from a complete LBK graveyard at Derenburg Meerenstieg II in Germany. These results considerably extend the available genetic dataset for the LBK (n = 42) and permit the first detailed genetic analysis of the earliest Neolithic culture in Central Europe (5,500-4,900 calibrated B.C.). We characterized the Neolithic mitochondrial DNA sequence diversity and geographical affinities of the early farmers using a large database of extant Western Eurasian populations (n = 23,394) and a wide range of population genetic analyses including shared haplotype analyses, principal component analyses, multidimensional scaling, geographic mapping of genetic distances, and Bayesian Serial Simcoal analyses. The results reveal that the LBK population shared an affinity with the modern-day Near East and Anatolia, supporting a major genetic input from this area during the advent of farming in Europe. However, the LBK population also showed unique genetic features including a clearly distinct distribution of mitochondrial haplogroup frequencies, confirming that major demographic events continued to take place in Europe after the early Neolithic.

Hit or miss - A metagenomic evaluation of intra-bone variability of host pathogen load in tuberculosis-infected human remains.

Many sampling protocols have been established to successfully retrieve human DNA from archaeological remains, however the systematic detection of ancient pathogens remains challenging. Here, we present a first assessment of the intra-bone variability of metagenomic composition in human skeletal remains and its effect on the sampling success for Mycobacterium tuberculosis (MTB) and human endogenous DNA. For this purpose, four bone samples from published peer-reviewed studies with PCR-based evidence for ancient MTB DNA were selected. Two bone samples of a Neolithic individual from Halberstadt, Germany and two ribs of two 18th-century Hungarian church mummies were sampled at multiple locations for equal amounts, followed by DNA extraction and library construction. Shotgun sequencing data was generated for taxonomic profiling as well as quantitative and qualitative evaluation of MTB and human endogenous DNA. Despite low variance in microbial diversity within and across samples, intra-bone variability of up to 36.45- and 62.88-fold for authentic ancient MTB and human reads, respectively, was detected. This study demonstrates the variable sampling success for MTB and human endogenous DNA within single skeletal samples despite relatively consistent microbial composition and highlights how a multisampling approach can facilitate the detection of hotspots with highly concentrated pathogen and human endogenous DNA.

Rib lesions in skeletons from early neolithic sites in Central Germany: on the trail of tuberculosis at the onset of agriculture.

As an infectious disease, tuberculosis (TB) is one of the major causes of death worldwide. Paleopathological and paleomicrobiological studies indicate a long standing association of the causative agent Mycobacterium tuberculosis and its human host. Since the occurrence and the epidemic spread of this pathogen seem to be closely linked to social and biological factors, it is of particular interest to understand better the role of TB during periods of social and nutritional change such as the Neolithic. In this study, 118 individuals from three sites in Saxony-Anhalt (Germany) dating to the Linear Pottery Culture (5400-4800 BC) were examined macroscopically to identify TB related bone lesions. In two individuals, Pott's disease was detected. In addition, periosteal reactions of varying degrees and frequency were observed mainly along the neck of the ribs in 6.5% (2/31) of subadults and 35.1% (20/57) of adults, with one site standing out markedly. Rib lesions, however, are not specific indicators of TB as they can also be caused by other diseases; so additional investigations were undertaken using histology and micro-CT scans to say more about the disease process. Supplementary molecular analyses indicate the presence of pathogens belonging to the Mycobacterium tuberculosis complex in individuals of all sites. Furthermore, we discuss the occurrence and spread of TB during the Neolithic with regard to nutritional aspects and possible risks of infection. The data presented provide important insights into the health status of Early Neolithic populations in Central Germany.

Bioarchaeological investigations of the princely grave at Helmsdorf attesting to the violent death of an Early Bronze Age leader.

The Helmsdorf "princely" tomb, excavated at the beginning of the twentieth century, is one of the most important archaeological discoveries dating from the Early Bronze Age in central Germany. In addition to the burial inventory, which points to an elevated social position of the deceased, a number of highly fragmented skeletal remains were preserved. Forensic anthropological investigation identified three distinctive bone defects, the surfaces of which were macromorphologically and microscopically examined in greater detail. Micro-CT analyses were also carried out. The results of all examinations suggested that the defects represented three perimortem injuries. The wound morphology was indicative of the use of a bladed weapon. The combination of injuries and their locations supported the assumption of a targeted use of force to kill. A comparison of Early Bronze Age weapons and tools with the bone lesions led to the identification of a type of weapon possibly used in the attack.

A Healthier Smile in the Past? Dental Caries and Diet in Early Neolithic Farming Communities from Central Germany.

Dental health is closely linked to an individual's health and diet. This bioarcheological study presents dental caries and stable isotope data obtained from prehistoric individuals (n = 101) from three Early Neolithic sites (c. 5500-4800 BCE) in central Germany. Dental caries and ante-mortem tooth loss (AMTL) were recorded and related to life history traits such as biological sex and age at death. Further, we correlate evidence on caries to carbon and nitrogen isotope data obtained from 83 individuals to assess the relationship between diet and caries. In 68.3% of the adults, carious lesions were present, with 10.3% of teeth affected. If AMTL is considered, the values increase by about 3%. The prevalence of subadults (18.4%) was significantly lower, with 1.8% carious teeth. The number of carious teeth correlated significantly with age but not sex. The isotopic data indicated an omnivorous terrestrial diet composed of domestic plants and animal derived protein but did not correlate with the prevalence of carious lesions. The combined evidence from caries and isotope analysis suggests a prevalence of starchy foods such as cereals in the diet of these early farmers, which aligns well with observations from other Early Neolithic sites but contrasts to Late Neolithic and Early Bronze Age populations in Germany.

Incremental lines in human acellular tooth cementum - New insights by SEM analysis.

BACKGROUND: Tooth cementum covers the surface of the root dentine and is produced and laid down in thin layers continuously throughout life. Functionally, different types of tooth cementum can be distinguished, which can be roughly divided into acellular (primary cementum) and cellular (secondary cementum) forms. One main type is acellular extrinsic fibre cementum (AEFC), which covers the cervical and middle third of the root. Light microscopic examinations of transverse sections of AEFC show lamellar patterns of alternating light and dark lines called growth or incremental lines. Following mammalian research, a seasonal rhythm of incremental line formation is also assumed in humans. Previous attempts at visualising incremental lines in the AEFC by scanning electron microscopy (SEM) were not particularly successful. The aim of the present study was to detect incremental lines in the AEFC and to analyse their underlying structure by SEM. METHODS: For this purpose, non-embedded and resin-embedded transverse and longitudinal sections of three single-rooted teeth obtained from different patients were investigated. The thin sections were not pre-treated (e.g. by etching, grinding or coating). RESULTS: Lamellar structures, which could be identified as incremental lines, were detectable in both transverse and longitudinal sections, with transverse orientation in the cross-section and longitudinal orientation in the longitudinal section. The lamellar pattern was created by broad fibre-rich layers alternating with narrow fibre-poor layers. The orientation of the collagen fibres changed from layer to layer from transverse to radial direction. The visibility of the layered structure discovered varied significantly. CONCLUSIONS: The study demonstrate that it is possible, in principle, to detect incremental lines in AEFC and to identify their basic structure using SEM. Our results suggest that the density and orientation of the fibres play an essential role in the formation of incremental lines. Functional aspects seem to be of particular importance.

Dental pulp calcifications in prehistoric and historical skeletal remains.

BACKGROUND: The prevalence of hard tissue formations in the dental pulp varies considerably. Beside ageing processes and irritations of the dental pulp, etiological associations with cardiovascular disease and dietary habits have been discussed, which are of particular research interest. The aim of this pilot study is to provide new insights on structural and etiological factors involved in the development of pulp calcifications by investigating skeletal remains from different (pre)historic periods. METHODS: The jaws of 46 skeletons excavated in central Germany, were examined for the presence of pulp stones using digital volume tomography (DVT). A total of 1122 teeth were examined with all tooth types considered. To obtain information about the three-dimensional structure of pulp calcifications, micro-CT images were taken. Thin sections of three molars were histologically analysed. Potential dietary effects were studied by analysing stable isotope ratios of nitrogen (δ15N) in bone samples collected from each individual. RESULTS: The analysis indicates that pulp stones affect molars in particular and increase slightly with age and dental wear. The micro-CT scans and the histological analysis show that the structures are much more complex than presumed on the basis of DVT imaging. Individuals with lower δ15N-isotope values and thus with a potentially lower proportion of animal protein in their diet appear to be less affected by pulp stones. CONCLUSION: When comparing between archaeological and recent data, DVT analysis provides qualitatively comparable results. Micro-CT and histological images illustrate the excellent preservation of pulp calcifications and their complex structure. Differences in prevalence rates and δ15N-isotope values of Neolithic and historical individuals support the assumption that dietary habits and living conditions could have an influence on the development of pulp calcifications. Due to the small sample size these results require further validation.

A massacre of early Neolithic farmers in the high Pyrenees at Els Trocs, Spain.

Violence seems deeply rooted in human nature and an endemic potential for such is today frequently associated with differing ethnic, religious or socio-economic backgrounds. Ethnic nepotism is believed to be one of the main causes of inter-group violence in multi-ethnic societies. At the site of Els Trocs in the Spanish Pyrenees, rivalling groups of either migrating early farmers or farmers and indigenous hunter-gatherers collided violently around 5300 BCE. This clash apparently resulted in a massacre of the Els Trocs farmers. The overkill reaction was possibly triggered by xenophobia or massive disputes over resources or privileges. In the present, violence and xenophobia are controlled and sanctioned through social codes of conduct and institutions. So that, rather than representing an insurmountable evolutionary inheritance, violence and ethnic nepotism can be overcome and a sustainable future achieved through mutual respect, tolerance and openness to multi-ethnic societies.

Early Neolithic executions indicated by clustered cranial trauma in the mass grave of Halberstadt.

The later phase of the Central European Early Neolithic witnessed a rise in collective lethal violence to a level undocumented up to this date. This is evidenced by repeated massacres of settled communities of the Linearbandkeramik (ca. 5600-4900 cal BC), the first full farming culture in this area. Skeletal remains of several dozen victims of this prehistoric warfare are known from different sites in Germany and Austria. Here we show that the mass grave of Halberstadt, Germany, a new mass fatality site from the same period, reveals further and so far unknown facets of Early Neolithic collective lethal violence. A highly selected, almost exclusively adult male and non-local population sample was killed by targeted blows to the back of the head, indicating a practice of systematic execution under largely controlled conditions followed by careless disposal of the bodies. This discovery significantly increases current knowledge about warfare-related violent behaviour in Early Neolithic Central Europe.

4000 years of human dietary evolution in central Germany, from the first farmers to the first elites.

Investigation of human diet during the Neolithic has often been limited to a few archaeological cultures or single sites. In order to provide insight into the development of human food consumption and husbandry strategies, our study explores bone collagen carbon and nitrogen isotope data from 466 human and 105 faunal individuals from 26 sites in central Germany. It is the most extensive data set to date from an enclosed geographic microregion, covering 4,000 years of agricultural history from the Early Neolithic to the Early Bronze Age. The animal data show that a variety of pastures and dietary resources were explored, but that these changed remarkably little over time. In the human δ15N however we found a significant increase with time across the different archaeological cultures. This trend could be observed in all time periods and archaeological cultures (Bell Beaker phenomenon excluded), even on continuously populated sites. Since there was no such trend in faunal isotope values, we were able largely to exclude manuring as the cause of this effect. Based on the rich interdisciplinary data from this region and archaeological period we can argue that meat consumption increased with the increasing duration of farming subsistence. In δ13C, we could not observe any clear increasing or decreasing trends during the archaeological time periods, either for humans or for animals, which would have suggested significant changes in the environment and landscape use. We discovered sex-related dietary differences, with males of all archaeological periods having higher δ15N values than females, and an age-related increasing consumption of animal protein. An initial decrease of δ15N-values at the age of 1-2 years reveals partial weaning, while complete weaning took place at the age of 3-4 years.

Neolithic and medieval virus genomes reveal complex evolution of hepatitis B.

The hepatitis B virus (HBV) is one of the most widespread human pathogens known today, yet its origin and evolutionary history are still unclear and controversial. Here, we report the analysis of three ancient HBV genomes recovered from human skeletons found at three different archaeological sites in Germany. We reconstructed two Neolithic and one medieval HBV genome by de novo assembly from shotgun DNA sequencing data. Additionally, we observed HBV-specific peptides using paleo-proteomics. Our results demonstrated that HBV has circulated in the European population for at least 7000 years. The Neolithic HBV genomes show a high genomic similarity to each other. In a phylogenetic network, they do not group with any human-associated HBV genome and are most closely related to those infecting African non-human primates. The ancient viruses appear to represent distinct lineages that have no close relatives today and possibly went extinct. Our results reveal the great potential of ancient DNA from human skeletons in order to study the long-time evolution of blood borne viruses.

A historical case of beaten-copper cranium.

The authors present the oldest historical case of a so-called beaten-copper cranium. The typical pattern was identified on a skull from a child, probably a boy, who died at approximately 6 years of age and was buried in a provisional cemetery used during the siege of Hanau, Germany, in 1635 and 1636. Morphological and radiological analyses of the severe digitate impressions ubiquitous on the child's endocranium support the diagnosis of chronically elevated intracranial pressure due to hydrocephalus.

The face of war: Trauma analysis of a mass grave from the Battle of Lützen (1632).

Contemporary accounts of battles are often incomplete or even erroneous because they reflect the-often biased-viewpoints of the authors. Battlefield archaeology faces the task of compiling an historical analysis of a battle and of gathering all the available facts. Besides cultural historical evidence and artefacts, the human remains of those who have fallen in battle also provide invaluable information. In studying mass graves from a military context, the injury types and patterns are significant. They allow us to reconstruct the circumstances surrounding the soldiers' deaths and provide information on the hostilities that occurred on the battlefield. One such mass grave was discovered in 2011 at Lützen, Saxony-Anhalt (Germany). Based on its geographical location and on the results obtained from archaeological examinations carried out in the area, the grave could be dated to the Thirty Years War (1618-1648). Further archaeological research confirmed that the dead had been soldiers from the Battle of Lützen (1632). The mass grave was block-lifted and then comprehensively examined at the State Museum of Prehistory in Halle (Saale). As well as osteological examinations to determine age, sex, height, state of health, i.e. diseases or injuries, imaging methods were also employed and histological and isotopic analyses carried out. The focus of this study was on the injuries sustained by the soldiers both prior to and during the battle. The results revealed that the 47 deceased had been between the ages of 15 and 50 when they died. Numerous healed injuries showed that the men had often been involved in violent encounters. Approximately three in every four soldiers had injuries that could have been fatal. Wounds inflicted by handguns, particularly to the skull, were predominant. The integrative analysis of the archaeological and anthropological data allowed us to conclude that the majority had been killed during a cavalry attack.

Holes in teeth - Dental caries in Neolithic and Early Bronze Age populations in Central Germany.

This study provides diachronic insight into the epidemiology of carious defects in teeth of Neolithic and Early Bronze Age populations in Central Germany over a period of 4000 years. The data were retrieved from skeletal remains uncovered at 21 sites throughout the Middle Elbe-Saale region (MES), comprising a total of 494 individuals with preserved teeth. The data generated were examined for age- and sex-related differences in order to gain information about the dietary habits and socio-economic structures of the period with the goal of identifying potential diachronic changes. The results indicated that dietary habits changed over the course of the Neolithic period: the prevalence of caries significantly decreased between the Early and Late Neolithic. The adults from the Early Neolithic sample, particularly those from the LBK bore the highest rate of caries. This highlights the essential importance of cereals in the diet of the early farmers in the Middle Elbe-Saale region. As time went on, meat and dairy products became more and more important, which had a positive impact on dental health. The data also show sex-specific differences: women were more often affected by caries than men and female jaws also generally exhibited greater numbers of carious teeth than their male counterparts. Dental health is a reflection of both biological factors and of economic and sociocultural structures.