Huber Rebekah S, Kim Namkug, Renshaw Carl E, Renshaw Perry F, Kondo Douglas G
The Brain Institute, University of Utah, Salt Lake City, USA.
Department of Earth Sciences, Dartmouth College, Hanover, USA.
Geospat Health. 2014 Nov;9(1):231-5. doi: 10.4081/gh.2014.20.
Therapeutic dosages of lithium are known to reduce suicide rates, which has led to investigations of confounding environmental risk factors for suicide such as lithium in groundwater. It has been speculated that this might play a role in the potential relationship between suicide and altitude. A recent study in Austria involving geospatial analysis of lithium in groundwater and suicide found lower levels of lithium at higher altitudes. Since there is no reason to suspect this correlation is universal given variation in geology, the current study set out to investigate the relationship between altitude and lithium in groundwater in the United States of America (USA). The study utilised data extracted from the National Water-Quality Assessment programme implemented by the United States Geological Survey that has collected 5,183 samples from 48 study areas in USA for the period of 1992 to 2003. Lithium was the trace-element of interest and 518 samples were used in the current analyses. Due to uneven lithium sampling within the country, only the states (n=15) with the highest number of lithium samples were included. Federal information processing standard codes were used to match data by county with the mean county altitude calculated using altitude data from the Shuttle Radar Topography Mission. The study was controlled for potential confounding factors known to affect levels of lithium in groundwater including aquifer, aquifer type, lithology, water level and the depths of wells. The levels of lithium in groundwater, increased with altitude (R(2) = 0.226, P <0.001) during the study period. These findings differ from the Austrian study and suggest a need for further research accounting also for the impact of geographical variation.
已知锂的治疗剂量可降低自杀率，这引发了对自杀的混杂环境风险因素的调查，比如地下水中的锂。有人推测，这可能在自杀与海拔之间的潜在关系中起作用。奥地利最近一项涉及对地下水中锂和自杀情况进行地理空间分析的研究发现，海拔越高，锂含量越低。鉴于地质情况存在差异，没有理由怀疑这种相关性具有普遍性，因此当前这项研究着手调查美国地下水中海拔与锂之间的关系。该研究利用了从美国地质调查局实施的国家水质评估计划中提取的数据，该计划在1992年至2003年期间从美国48个研究区域采集了5183个样本。锂是研究关注的微量元素，当前分析使用了518个样本。由于该国锂采样不均衡，仅纳入了锂样本数量最多的15个州。使用联邦信息处理标准代码，按县将数据与利用航天飞机雷达地形测绘任务的海拔数据计算得出的县平均海拔进行匹配。该研究对已知会影响地下水中锂含量的潜在混杂因素进行了控制分析，这些因素包括含水层、含水层类型、岩性、水位和井深。在研究期间，地下水中的锂含量随海拔升高而增加（R² = 0.226，P <0.001）。这些发现与奥地利的研究不同，表明还需要进一步研究地理差异的影响。
