Tarquini B, Perfetto F, Tarquini R
Istituto di Clinica Medica IV, Università, Firenze.
Recenti Prog Med. 1998 Jul-Aug;89(7-8):395-403.
Melatonin (MEL) hypothesis in seasonal affective disorders (SAD) is supported by: a) historical hint; b) circadian and seasonal MEL periodicity with evidence that the SAD is related to photoperiod; c) relationship between incidence and severity of SAD and latitude; d) the response to bright artificial light (ineffective in depression) which mimics summer time; e) MEL administration can induce some symptoms of the SAD; f) several antidepressant drugs increase MEL plasma levels. Several of these findings are disproved: the light acts independently from the MEL, some antidepressant agents act without modifying MEL levels; a consistent alteration in MEL secretion within SAD has not been convincingly demonstrated. Relationship between incidence and severity of SAD and latitude suggests a new potential implication of MEL in SAD. The daytime melatonin values reflect changes along the scale of a year in sunshine. Accordingly, the about-yearly periodicity, much larger in amplitude than the half-yearly component, yields ratios smaller than unity. By contrast during darkness an about-half-yearly component is more prominent. As the aurora zone is approached, the intensity of magnetic disturbances increases. Thus, the intensity of these two variables shows inverse relationships with latitude and geomagnetic field decreases plasma levels of MEL and inhibits MEL function.
季节性情感障碍（SAD）中的褪黑素（MEL）假说得到以下支持：a）历史线索；b）昼夜和季节性的MEL周期性，且有证据表明SAD与光周期有关；c）SAD的发病率和严重程度与纬度之间的关系；d）对模拟夏季的明亮人造光的反应（对抑郁症无效）；e）给予MEL可诱发SAD的一些症状；f）几种抗抑郁药物可提高血浆MEL水平。其中一些发现被反驳：光的作用独立于MEL，一些抗抑郁药在不改变MEL水平的情况下起作用；尚未令人信服地证明SAD患者的MEL分泌存在一致的改变。SAD的发病率和严重程度与纬度之间的关系表明MEL在SAD中具有新的潜在意义。白天的褪黑素值反映了一年中日照时间的变化。因此，大约每年的周期性，其幅度比半年的分量大得多，产生的比率小于1。相比之下，在黑暗中，大约半年的分量更为突出。随着接近极光区，磁干扰强度增加。因此，这两个变量的强度与纬度呈反比关系，地磁场降低MEL的血浆水平并抑制MEL功能。
