Here are seven recent research studies - largely about the effects of early life adversity on adult psychological health (although I've slipped in one I find important on the prevalence & effects of subsyndromal/subclinical symptoms).  The last two papers touch on the truth or falsity of Nietsche's famous saying "What does not destroy me makes me stronger".

So Joni & colleagues highlight the long term sequelae of childhood adversity in their paper "Children's problems predict adults' DSM-IV disorders across 24 years" (abstracts & links for all papers mentioned are given further down this post).  Kessler et al go further, examining associations of 12 childhood adversities with first onset of 20 DSM-IV disorders in 51,945 adults across 21 countries.  They found that "Childhood adversities associated with maladaptive family functioning (e.g. parental mental illness, child abuse, neglect) were the strongest predictors of disorders ... Childhood adversities account for 29.8% of all disorders across countries."  Meanwhile Dynum et al assessed how common childhood adverse experiences (ACEs) were in the USA by surveying 26,229 adults across 5 US states. Worryingly they found that "59.4% of respondents reported having at least one ACE, and 8.7% reported five or more ACEs. The high prevalence of ACEs underscores the need for 1) additional efforts at the state and local level to reduce and prevent child maltreatment and associated family dysfunction and 2) further development and dissemination of trauma-focused services to treat stress-related health outcomes associated with ACEs."  For more on the importance & assessment of ACEs see further down this website's "Good knowledge" page "Life review, traumatic memories & therapeutic writing".  And it's not just resulting full psychiatric (or physical) disorders that are relevant, subsyndromal disorders are also very common, disabling and costly to individuals and to society - see Rai et al's UK-based study "Common mental disorders, subthreshold symptoms and disability: longitudinal study."   

And lastly a bit of somewhat encouraging news relevant to the Nietsche quote above, two papers by Seery & colleagues show "Exposure to adverse life events typically predicts subsequent negative effects on mental health and well-being, such that more adversity predicts worse outcomes. However, adverse experiences may also foster subsequent resilience, with resulting advantages for mental health and well-being. In a multiyear longitudinal study of a national sample, people with a history of some lifetime adversity reported better mental health and well-being outcomes than not only people with a high history of adversity but also than people with no history of adversity. Specifically, U-shaped quadratic relationships indicated that a history of some but nonzero lifetime adversity predicted relatively lower global distress, lower self-rated functional impairment, fewer posttraumatic stress symptoms, and higher life satisfaction over time. Furthermore, people with some prior lifetime adversity were the least affected by recent adverse events. These results suggest that, in moderation, whatever does not kill us may indeed make us stronger."  

Joni, R., M. Inge van, et al. (2010). "Children's Problems Predict Adults' DSM-IV Disorders Across 24 Years." Journal of the American Academy of Child and Adolescent Psychiatry 49(11): 1117-1124.  [Abstract/Full Text]  
The goal of this study was to determine continuities of a broad range of psychopathology from childhood into middle adulthood in a general population sample across a 24-year follow-up. In 1983, parent ratings of children's problems were collected with the Child Behavior Checklist (CBCL) in a general population sample of 2,076 children and young adolescents aged 4 to 16 years. In 2007, 24 years later, 1,339 of these individuals were reassessed with the CIDI, a standardized DSM-IV interview. We used univariate logistic regression analyses to determine the associations between children's problems and adults' psychiatric disorders. Parent reported total problems scores in the deviant range (>85th percentile) predicted disruptive disorders in adulthood (odds ratio [OR] = 1.7, 95% confidence interval [95% CI] = 1.1-2.8). Adjusted for sex, age, and socioeconomic status in all analyses, deviant levels of parent-reported childhood anxiety predicted anxiety disorders in middle adulthood (OR = 1.6, 95% CI = 1.0-2.5). Conduct problems (i.e., cruelty to animals, lies) predicted both mood disorders (OR = 2.3, 95% CI = 1.1-4.8) and disruptive disorders (OR 2.1, 95% CI = 1.3-3.4), whereas oppositional defiant problems predicted only mood disorders (OR = 2.3, 95% CI = 1.0-5.2). Attention-deficit/hyperactivity problems did not predict any of the DSM-IV disorders in adulthood (OR = 0.8, 95% CI = 0.5-1.2). Children with psychopathology are at greater risk for meeting criteria for DSM-IV diagnoses in adulthood than children without psychopathology, even after 24 years. Moreover, different types of continuities of children's psychopathology exist across the lifespan. We found that anxious children, oppositional defiant children, and children with conduct problems are at greater risk for adult psychopathology. Effective identification and treatment of children with these problems may reduce long-term continuity of psychopathology.

Kessler, R. C., K. A. McLaughlin, et al. (2010). "Childhood adversities and adult psychopathology in the WHO World Mental Health Surveys." The British Journal of Psychiatry 197(5): 378-385.  [Abstract/Full Text]  
Background Although significant associations of childhood adversities with adult mental disorders are widely documented, most studies focus on single childhood adversities predicting single disorders. Aims To examine joint associations of 12 childhood adversities with first onset of 20 DSM-IV disorders in World Mental Health (WMH) Surveys in 21 countries. Method Nationally or regionally representative surveys of 51,945 adults assessed childhood adversities and lifetime DSM-IV disorders with the WHO Composite International Diagnostic Interview (CIDI). Results Childhood adversities were highly prevalent and interrelated. Childhood adversities associated with maladaptive family functioning (e.g. parental mental illness, child abuse, neglect) were the strongest predictors of disorders. Co-occurring childhood adversities associated with maladaptive family functioning had significant subadditive predictive associations and little specificity across disorders. Childhood adversities account for 29.8% of all disorders across countries. Conclusions Childhood adversities have strong associations with all classes of disorders at all life-course stages in all groups of WMH countries. Long-term associations imply the existence of as-yet undetermined mediators.

Bynum, L., T. Griffin, et al. (2010). "Adverse Childhood Experiences Reported by Adults --- Five States, 2009." Morbidity and Mortality Weekly Report 59(49): 1609-1613.  [Abstract/Full Text] 
Adverse childhood experiences (ACEs) include verbal, physical, or sexual abuse, as well as family dysfunction (e.g., an incarcerated, mentally ill, or substance-abusing family member; domestic violence; or absence of a parent because of divorce or separation). ACEs have been linked to a range of adverse health outcomes in adulthood, including substance abuse, depression, cardiovascular disease, diabetes, cancer, and premature mortality. Furthermore, data collected from a large sample of health maintenance organization members indicated that a history of ACEs is common among adults and ACEs are themselves interrelated (4). To examine whether a history of ACEs was common in a randomly selected population, CDC analyzed information from 26,229 adults in five states using the 2009 ACE module of the Behavioral Risk Factor Surveillance System (BRFSS). This report describes the results of that analysis, which indicated that, overall, 59.4% of respondents reported having at least one ACE, and 8.7% reported five or more ACEs. The high prevalence of ACEs underscores the need for 1) additional efforts at the state and local level to reduce and prevent child maltreatment and associated family dysfunction and 2) further development and dissemination of trauma-focused services to treat stress-related health outcomes associated with ACEs.

Rai, D., P. Skapinakis, et al. (2010). "Common mental disorders, subthreshold symptoms and disability: longitudinal study." The British Journal of Psychiatry 197(5): 411-412.  [Abstract/Full Text] 
In a representative sample of the UK population we found that common mental disorders (as a group and in ICD-10 diagnostic categories) and subthreshold psychiatric symptoms at baseline were both independently associated with new-onset functional disability and significant days lost from work at 18-month follow-up. Subthreshold symptoms contributed to almost half the aggregate burden of functional disability and over 32 million days lost from work in the year preceding the study. Leaving these symptoms unaccounted for in surveys may lead to gross underestimation of disability related to psychiatric morbidity.

Seery, M. D., E. A. Holman, et al. (2010). "Whatever does not kill us: Cumulative lifetime adversity, vulnerability, and resilience." Journal of Personality and Social Psychology 99(6): 1025-1041.  [PubMed] 
Exposure to adverse life events typically predicts subsequent negative effects on mental health and well-being, such that more adversity predicts worse outcomes. However, adverse experiences may also foster subsequent resilience, with resulting advantages for mental health and well-being. In a multiyear longitudinal study of a national sample, people with a history of some lifetime adversity reported better mental health and well-being outcomes than not only people with a high history of adversity but also than people with no history of adversity. Specifically, U-shaped quadratic relationships indicated that a history of some but nonzero lifetime adversity predicted relatively lower global distress, lower self-rated functional impairment, fewer posttraumatic stress symptoms, and higher life satisfaction over time. Furthermore, people with some prior lifetime adversity were the least affected by recent adverse events. These results suggest that, in moderation, whatever does not kill us may indeed make us stronger.

Seery, M. D., R. J. Leo, et al. (2010). "Lifetime exposure to adversity predicts functional impairment and healthcare utilization among individuals with chronic back pain." Pain 150(3): 507-515.  [PubMed] 
Previous research has demonstrated an association between lifetime exposure to adverse events and chronic back pain (CBP), but the nature of this relationship has not been fully specified. Adversity exposure typically predicts undesirable outcomes, suggesting that lack of all adversity is optimal. However, we hypothesized that among individuals faced with CBP, a history of a low level of lifetime adversity would yield protective effects, manifested as lower impairment and healthcare utilization. Adult members of a national panel (N=396) endorsed a history of CBP when reporting their physical health status in an online survey; they further reported their functional impairment and healthcare utilization. Respondents had previously completed a survey of lifetime exposure to adverse events. Significant U-shaped quadratic relationships emerged between adversity and self-rated functional impairment (p<0.001), disabled employment status (p<0.001), frequency of physician/clinic visits for CBP (p<0.01), prescription (but not over-the-counter) analgesic use (p<0.01), and comorbid depression treatment seeking (p<0.01). Specifically, people with some lifetime adversity reported less impairment and healthcare utilization than people who had experienced either no adversity or a high level of adversity. Additional analyses failed to support alternative explanations of the findings. Implications for understanding and promoting resilience in the context of CBP are discussed.