What is the scientific basis for long-term negative physiological effects of overstudying? I am interested in long term negative physiological effects that some students experience following overstudying. 


What is the scientific basis for overstudying?
Is over studying correlated with long term decreases of cognitive ability?
The research literature on stress in general and burnout in particular would be relevant. The stress literature is massive and there are studies that have a particular focus on students.

For example Jacobs and Dodd did a study on college student burnout:


  Measures of social support (Multidimen- sional Scale of Perceived
  Social Support), personality (General Temperament Survey), and
  workload were related to psychological burnout (Maslach Burnout
  Inventory) among 149 college students ( M = 20.8 yrs.). High levels of
  burnout were predicted by negative temperament and subjective
  workload, but actual workload (academic and vocational) had little to
  do with burnout. Low levels of burnout were predicted by positive
  tempera- ment, participation in extracurricular activities, and social
  support, especially from friends.


They also cite some of the literature on stress in college  students:


  there has been a substantial amount of research on
  stress among general college students. Stress has been shown to be
  correlated with college students’ health behaviors (Weidner, Kohl-
  mann, Dotzauer, &amp; Burns, 1996), anxiety concerning exams (Abouserie,
  1994; Ever- son, Tobias, Hartman, &amp; Gourgey, 1993; Sloboda, 1990),
  self-esteem (Abouserie; Newby-Fraser &amp; Schlebusch, 1997), and coping
  strategies that students use (Dwyer &amp; Cummings, 2001). To the extent
  that stress is an important component of burnout (Maslach &amp; Jackson,
  1981), this research is relevant to the development of a model of
  burnout among college students. Between classes, exams, employment,
  and extra- curricular activities, students are likely to experience
  high levels of stress, but do they experience burnout? Much research
  is needed to determine the prevalence of burnout, to identify
  important intrapersonal and interpersonal factors that influence
  burnout, and to develop effective inter- ventions to prevent and
  reduce burnout in college students.


References


Jacobs, S.R. &amp; Dodd, D. (2003). Student burnout as a function of personality, social support, and workload. Journal of College Student Development, 44, 291-303.