Specifically, the stress of experiencing CM has been linked to HPA dysregulation during the period of maltreatment as well as until adulthood 17. Ongoing stress and stress of which the individual is not able to effectively cope with may change the sensitivity of the glucocorticoid receptors, resulting in alterations in cortisol delivery and affects other brain structures such as the hippocampus 18. Several studies have examined the effect of CM showing that individuals with CM experiences demonstrate dysregulated cortisol levels measured in urine, blood and saliva 1920. Morris and colleagues (2012) showed that adults, who were maltreated as children, tend to exhibit lower levels of cortisol in the evening 21 and blunted responsiveness to psychosocial challenges 22. In contrast, Heim et al. identified increased cortisol responsiveness to challenge in context of CM 23. Especially in maltreated children, the research findings are less clear 24 revealing increased, decreased or similar patterns of cortisol reactivity compared to a non-maltreated control group 17. In detail, Cicchetti and Rogosch (2001) and Bruce and colleagues (2009) detected that physically abused children showed lower salivary cortisol levels and flattened diurnal slope 2526 indicating a down-regulation of the HPA axis in response to initial cortisol increasing the context of CM 18. Both, boys and girls with CM experiences showed attenuated cortisol stress responses in stressful situations 242728. In addition, studies of toddlers living in Russia and Romania showed decreased morning cortisol levels and no diurnal salivary cortisol decrease throughout the day 29. This has also been shown to be apparent among preschoolers in foster care, of which 35% showed blunted cortisol diurnal rhythm 30. In contrast to these findings, De Bellis et al. (1999) showed that children with experiences of CM and a consecutive posttraumatic stress disorder had increased cortisol levels 19. Furthermore, it has been shown that cortisol levels increased with the severity and duration of CM 12. Longitudinal studies of HPA axis regulation in maltreated individuals are rare 24. Nevertheless, one study realized a longitudinal HPA axis follow-up from childhood over adolescence to adulthood in maltreated girls. They reported high cortisol levels in childhood, attenuated cortisol in adolescence and exhibited low cortisol levels in adulthood 31, which suggest a shift from hypocortisolism in childhood to receptor down-regulation in adulthood in response to chronic stress 28.

Recently, a growing research interest has been focused on the biological correlates of trans-generational transmission of CM showing that maternal child abuse results in disturbances in the HPA axis in their offspring. Brand and colleagues (2010) detected that children of mothers with CM showed lower baseline cortisol compared to children of mothers without CM. Additionally, children of mothers of a combination of both, a history of early maternal abuse and comorbid post-traumatic stress disorder, were associated with greater increases in child’s cortisol levels 32. Fisher et al. (2007) observed in a 25 - year longitudinal study lower morning cortisol and modified cortisol release during the day in children of mothers´ with experiences of CM compared to children without CM experiences of their mothers 33.

The transmission of HPA axis dysregulation due to CM into the next generation was confirmed by Yehuda and colleagues (2005) who reported, that offspring of mothers with traumatic experiences in adulthood and PTSD showed significantly lower cortisol levels in saliva and blood compared to a control group 34.

In childhood sensitive, warm and responsive caregiving plays an equivalent role in successful child’s behavioral and physiological regulation outcomes 35. High quality of caregiving is critical in reducing young infants´ distress in situations of emotional arousal and may buffer infant´s HPA axis response during stress 18. Extensive evidence of research findings indicates that excessive or prolonged activation of stress response in the first years of infants' life predicts later psychophysiological healing. It is particularly important to differ between types of stress: positive stress, tolerable stress and toxic stress. Infants could cope with both types of stress like positive stress as well as tolerable stress with moderate, short-lived stress responses respectively stress with potential to negatively affect but over limited time periods. Especially toxic stress in childhood revealed correlations with emotional behavior, health across lifespan and promotes damaging effects on learning 3637. Recently, physiological parameters have been used to confirm behavioral observations and to enable a more basal understanding of the relation between behavioral and physiological systems. The HPA axis stress response has been used to study physiological stress responsiveness to arousing or stressful situations in humans and animals 3839. The adrenocortical system seems to be particularly responsive to aversive or stressful situations that convey novelty or uncertainty accompanied by negative emotions 48. The earliest years in infants´ life are well known to be a critical window for disturbances in stress regulation processes. Both, sensitive and intrusive maternal interacting behaviors in free play and stressful situations have been associated with alterations of infants´ stress regulation outcomes 39. Especially the daily quality of caregiving may affect the development of infant’s stress regulatory capacities 174053. Gunnar et al. (1992) found associations between the quality of caregiving and the adrenocortical response of the infant during a paradigm of separation of mother and infant. Their findings suggested that caregiving might buffer the adrenocortical response of the infant in stressful situations 41. These findings were replicated by Enlow et al. (2014), who found that higher maternal insensitivity was associated with higher cortisol release during a stressful laboratory paradigm 42. This was confirmed by Haley et al. 2003 who reported that infants of more responsive parents showed greater regulation like lower peaks of cortisol in stress situations in their HPA stress response than infants of less responsive parents 43. In contrast Nachmias et al. (1996) showed no cortisol increase during an experimental setting of live clown in children of more sensitive parents compared to lower sensitive caregiving 44. On the other hand a high quality of caregiving is supposed enhance secure attachment between child and caregiver 55, and children who are securely attached showed no anomalous elevation of cortisol reaction when the attachment figure was present 464748. Cicchetti et al. suggested sensitive caregiving to play a major role on infants´ HPA axis regulation 49. However, there are only few comparative studies focusing on both, maternal behavior and maltreatment and their effects on infants´ HPA axis reactivity during stressful situations 50. For example Martinez-Torteya (2014) evaluated the effect of maternal parenting on infant’s biobehavioral regulation among maternal CM 51. They found no direct influence of infants´ physiological or behavioral responses but positive associations between maternal interaction quality and infant´s cortisol reactivity to stressors 51. Our investigations may shed light on the influence of maternal CM and the quality of caregiving on infants´ stress response one year after birth. Especially, the question of a transgenerational transmission of CM on behavior level should be clarified. Therefore, we aimed to differentiate maternal CM and caregiving on child’s cortisol stress reactivity and measured salivary cortisol in the mothers-child-dyad during the SSP. We hypothesized 1. that maternal cortisol response during SSP differs between mothers´ with and without CM and 2. that the cortisol response of the child will be transmitted by interacting behavior of the mothers´ in the first year of life and not by the history of maternal CM.

TRANS-GEN is an interdisciplinary study consortium investigating in a prospective approach the pathways leading to resilience or vulnerability in the transgenerational transmission of childhood maltreatment (CM) by focusing psychological, biological and social factors.

The study was funded by the Federal Ministry of Education and Research and was approved by the Ethics Committee of Ulm University. After recruiting in the maternity unit of the Ulm University Hospital all mother-infant dyads were followed up twice: 3 months (t1) and 12 months (t2) after birth.

For measuring the quality of maternal interactive behavior we videotaped mother-infant interactions during the SSP analyzed by the “Atypical Maternal Behavior Instrument for Assessment and Classification (AMBIANCE)” (AMBIANCE;55). The AMBIANCE is based on the theory of Main and Hesse (1990) and has been developed by Lyons-Ruth and colleagues and assesses anomalous parental behavior of mothers´ during interactions with their infant 555657.

Additionally to the concepts of frightened and frightening behaviors and dissociated parental states described by Main and Hesse 56 AMBIANCE considers profound disruptions in mother – infant interaction as well as behaviors that are physically or emotionally withdrawn 58. To assess the quality of interacting behavior AMBIANCE codes disrupted maternal behaviors on five dimensions: affective communication errors, role/boundary confusion, disorganized/ disoriented behaviors, negative/intrusive behavior, and withdrawal. Each dimension is coded on a 7-point scale as well as an overall score of the level of disruption. The frequency and intensity of all disrupted behaviors mothers´ displayed in the course of the interaction with their infant resulted in the level of maternal disrupted communication. Maternal disrupted communication coded up to 4 has been considered “not-disrupted” whereas a level from 5 to 7 is considered “disrupted”. Therefore, mothers with maternal communication below 5 were coded as “not-disrupted” whereas mothers coded from 5 till 7 were coded as “disrupted” mothers. All videotaped play sessions were scored by a single coder, who was blind to all other data of the mother-infant-dyads. This coder was trained by and reliable with the original developers of the AMBIANCE 55.

Descriptive statistics are shown in Table 1. Twenty-eight of 53 mothers were grouped as CM+ and 21 showed “disrupted” maternal behavior (Table 2 and Table 3). No significant differences were detected between the CM- and CM+ mothers as well as “non-disrupted” and the “disrupted” maternal behavior group concerning infant’s sex, mother’s age at birth and body mass indexes and thus were not considered for further analyses. There were also no significant differences for maternal interacting behavior focusing maternal education as well as their current marriage status.

Focusing maternal HPA axis reactivity during SSP by using ANCOVA for repeated measures, neither main time (F (1.392; 71.008) = 0.579, p= 0.503), nor group effects (F (1; 207.539) = 1.052, p= 0.310) were detectable for CM+ compared to CM-. The values showed marginal, but no significant differences for group-by-time effects (F (1.392; 71.008) = 3.157, p= 0.066) (Figure 1a).

For infant´s HPA axis time effects (F (2.226; 109.096) = 14.277, p= 0.000) could be shown. For infant’s main group-by-time (F (2.226; 109.096) = 0.595, p= 0.571) or group effects (F (1; 49) = 0.740, p= 0.394), no significant results were detectable (Figure 1b).

T-test analyses comparing two independent samples revealed no differences focusing maternal and infant´s cortisol values and CM for each of the measurements (baseline before SSP - +30 min.).

Using ANCOVA for repeated measures the saliva cortisol in mothers relative to maternal interacting behavior showed neither main time (F (1.398; 71.305) = 0.663, p= 0.466), group-by-time (F (1.398; 71.305) = 1.097, p= 0.320) nor group effects (F (1; 51) = 0.053, p= 0.819) (Figure 2a).

Saliva cortisol in their infants, however, showed significant time (F (3; 147) = 16.472, p= 0.000) as well as significant main group-by-time effects (F (3; 147) = 2.897, p= 0.048). For main group effects no significant differences could be shown (F (1; 49) = 1.664, p= 0.203) (Figure 2b).

T-test analyses comparing two independent samples showed no differences for maternal cortisol levels focusing maternal interacting behavior. For infants cortisol values differences could be shown for the measurement 15 minutes after SSP (+15 min.) (t(49) = -2.108, p = 0.040). Infants of mothers with lower sensitive caregiving showed significant higher cortisol values (M = 6.46, SD = 3.525)than infants of mothers with a higher sensitive interacting behavior (M = 9.613, SD = 7.051).

Focusing the infant’s cortisol response in association to maternal CM we could not find any differences between both groups of infants with and without maternal CM. This is in line with Martinez-Torteya et al. (2014) who found no direct association between maternal CM and infant’s cortisol reactivity after stressors 51. However, two longitudinal studies of Fisher et al. (2007) and Brand et al. (2010) described differences in baseline cortisol levels as well as modified cortisol release during the day in infants of mothers´ with experiences of CM compared to infants without maternal CM 3233. The divergence between our results and that of Fisher et al. (2007) and Brand et al. (2010) may be explained by the low severity of maternal CM load in our sample. Fisher et al. (2007) and Brand et al. (2010) measured a sample with a range from low to high maltreatment. In contrast to that, our sample showed only low to moderate maltreatment load. We might consider that severity of maternal CM load affects the transmission of own experiences of CM into the next generation. This is in accordance with Alink et al. (2012) who showed that the risk of dysregulation in cortisol levels of mothers with CM increased in dependence to the severity and the duration of CM 12. Therefore, we conclude that lower CM experiences in our sample may lead to a lower risk for transgenerational transmission of HPA axis dysregulations.

Interestingly, our data showed that maternal interacting quality seems to be a main factor that influence the infant´s cortisol stress regulation. Infants of mothers´ with disruptive interacting behavior showed a significant peak of cortisol level after 15 minutes compared to infants of mothers with sensitive interacting behavior. This indicates that enhanced sensitive caregiving resulted in lower infant’s cortisol stress response. The results are in line with previous studies showing that a higher quality of caregiving resulted in a reduced infant’s cortisol stress response 174651. Especially during the first years of life, infants need to manage the challenging transition from external regulation of affect and internal arousal to rising levels of psychobiological regulation 59. In attachment as well as developmental theory it is suggested that the quality of parental interacting behavior as well as the relationship between infants and parents are an important factor for the development of infant’s emotional and physiological regulatory strategies 4759.

The SSP is conceived as a stressful procedure in which the infant is stressed by two short separations from the caregiver. Several studies confirmed that the quality of maternal interacting behavior may buffer infants´ distress in situation of emotional arousal 60. A stable and reliable relationship between mother and infant based on maternal sensitive interacting behavior might reduce infants´ distress due to the SSP and stabilize the infant at the time of the reunion with the caregiver. Lower sensitive and supportive parenting (e.g. like frightening and anxious interaction behavior) might constrain or reduce the ability of physiological regulation, reflected by a dysregulation of infants’ cortisol stress response 4061.

Mothers´ with a history of CM showed no significant but marginal differences in course of their cortisol levels compared to mothers without CM. However mothers with a history of CM started with a lower but not significant differences in cortisol baseline than mothers without CM. This was also found by Trickett et al., (2010) who showed in a longitudinal design that adults maltreated in childhood showed lower cortisol baselines than adults without CM 31. Our findings show that the severity of experiencing CM may affect the regulation of the HPA axis until adulthood which is confirmed by data of Tarullo and Gunnar 17. One potential reason might be the moderate to low severity of CM load in our sample. Looking at maternal interacting quality there were no significant differences in the cortisol responses between disruptive and non-disruptive mothers. It seems that focusing differences in maternal interacting behavior in detail may not alter the cortisol reaction in mothers 21.

In summary, we did not find any cortisol-related transmission effects of CM to the next generation, however, maternal behavior seemed to play a crucial role in this context. This is a particularly important and encouraging finding with regard to the cycle of maltreatment and the fact that many parents are concerned to transmit their own experiences to their infants. Especially for parents with CM, the former experience of maltreatment was not as crucial like maternal daily interactions and the relationship with their infant. Inadequate or anomalous maternal interacting behavior may aggravate infants´ stress regulatory strategies, which could be a risk for later stress-related mental and physical burden linked to increased stress vulnerability and impaired emotion regulation 6263. Our results indicate that especially the daily experienced interacting quality by their mothers is relevant for the development of infant´s HPA stress regulation in the first year of life.

Therefore the findings of our analyses indicate both, protection and risk factors. On the one hand, maternal CM experience has been proven to affect cortisol stress response in adulthood. Especially mothers with CM experiences may be particularly vulnerable for dysregulated HPA axis. On the other hand, we were able to show that CM experience did not directly burden the next generation in terms of their stress regulation capacities. However, daily interactions between mother and infant contribute to the development of infants´ resilient stress responsiveness.

Limitations of this study were saliva acquisition problems due to mothers´ and infants´ limited amounts. This resulted in the small sample size of complete data sets. Additionally, in contrast to other studies with high maltreatment load our study showed a rather low severity of CM experiences. This has to be taken into account when comparing our results with other studies with samples showing wider range of CM experiences. Demographic characteristics of our sample can be considered as one limitation since the level of maternal education was high compared to other samples with history of CM.