Depressive symptoms are negative emotions caused by rumination and hopelessness due to the inability to cope with external pressure [29]. Previous studies provide strong evidence for the relationship between harsh parenting and depressive symptoms [33]. For example, a meta-analytic study conducted by Pinquart found that corporal punishment is positively related to adolescents’ depressive symptoms [34], and their depressive symptom levels increased over time. In addition, cross-sectional and longitudinal studies consistently show that harsh parenting may reduce adolescents’ expectations of future development, and thus increase their depressive symptoms [19,33].

COR theory provides a useful theoretical framework for understanding the relationship between harsh parenting and depressive symptoms. Adolescents who experienced harsh parenting must spend a lot of time and energy dealing with the negative results of harsh parenting (e.g., proving whether they deserve to be loved, whether their parents are satisfied with them, and whether they have done something wrong), which means that more emotional resources needed to be consumed by adolescents in the process of growing up [35,36]. Adolescents living with harsh parenting over time experience a lack of resources, resulting in adverse emotional reactions such as depressive symptoms [37]. In addition, harsh parenting is associated with limited parental support, making it difficult for these adolescents to obtain additional resources from the family [38], which further aggravates the lack of resources and leads to depressive symptoms [39]. In fact, research has shown that adolescents who experience harsh parenting are more likely to internalize this parenting style into failed support [40] and believe it will be difficult for them to obtain help from their family to deal with external pressure [41]. They form a negative view of themselves, resulting in a sense of low self-worth [17,33]. In view of this, as a stressful situation, harsh parenting is likely to trigger adolescent depressive symptoms.

Increasingly, studies are showing that depression is an important risk factor for suicidal ideation [42], though the relationship is complicated. Some studies argue that suicidal ideation is a depressive symptom; however, Kessler et al. clearly pointed out that they are two distinct constructs [43]. This is because depressive symptoms mainly reflect emotional problems, while suicidal ideation reflects a way of thinking and the formation of future plans. The former is likely a prerequisite for suicidal ideation, which exists before the latter [44]. According to the escape theory of suicide [45,46], adolescents who experience depressive symptoms may not be able to endure the intense sadness and a sense of worthlessness but may have the motivation to end their pain through suicidal ideation [47]. In a study on the relationship between depressive symptoms and suicidal ideation, scholars have suggested that adolescents induce a high level of suicidal ideation and implement it to escape pain because they cannot bear the low sense of self-worth brought about by their depressive symptoms [17]. To sum up, adolescents who experience harsh parenting are more likely to generate depressive symptoms, which may further lead to suicidal ideation.

According to COR theory [25,26], adolescents who have experienced harsh parenting are more likely to experience a resource loss spiral and then generate depressive symptoms, which can then cause suicidal ideation. Recently, research has indicated that individuals can prevent the loss of resources and acquire additional resources through personal level resource positive coping styles, to alleviate the negative impact of external pressure on themselves [48]. Research has suggested that mindfulness may reduce the negative effects of stress and trauma associated with adverse childhood exposures, improve short- and long-term outcomes, and potentially alleviate adverse health outcomes in adulthood [49].

In the present study, we propose that mindfulness, an important personal resource, may play a role in preventing a resource loss spiral and supplementing new resources for adolescents by helping them to break away from old experiences, decrease the automaticity of emotion, and increase their tolerance to negative emotions [50,51]. Accordingly, under the framework of the COR theory, this study introduces the construct of mindfulness as an important boundary condition to alleviate the negative effect of harsh parenting.

Among the protective factors to reduce mental health problems, the human ability to meditate may be an important factor. This cognitive process may represent mindfulness, which is stimulated by intentional attention to what is happening and a non-critical attitude [52]. In other words, mindfulness emphasizes openness and acceptance, and people experience all their thoughts and feelings in this process from a position of awareness and a lack of judgment [53,54].

This study assumes that mindfulness may weaken the effect of harsh parenting on depressive symptoms for several reasons. Mindfulness can effectively identify individual automatic thinking and unhealthy behavioral patterns, and assist individuals to form better affective regulation skills, thus enhancing their positive emotions and reducing negative emotions [50,55]. Therefore, mindfulness is likely to alleviate the facilitative effect of harsh parenting on depressive symptoms by encouraging adolescents to objectively experience and accept harsh parenting and regulate their negative emotional responses to harsh parenting [56].

Moreover, adolescents with high levels of mindfulness are inclined to consciously focus on their current experience [57,58], thus decreasing negative thoughts brought about by harsh parenting (e.g., a low sense of value and self-doubt). Mindfulness also helps adolescents to observe internal and external stimuli without judgment or evaluation [59], thereby enhancing their ability to discover additional resources (e.g., other individual resources and external resources) and alleviating the resource loss spiral. More available resources for adolescents are likely to lessen the accumulation of negative emotions and the generation of depressive symptoms [60]. As such, the effect of harsh parenting on depressive symptoms may be weaker in adolescents with high levels of mindfulness.

The present study presumes that adolescent mindfulness can mitigate the effects of harsh parenting on suicidal ideation in two ways. First, mindfulness can help adolescents to observe their thoughts and accept psychological and environmental events without judgment [61], so that they can recognize that the self-doubt and low sense of self-worth brought about by harsh parenting is only a feeling or thought, and not necessarily an accurate representation of the facts, thereby decreasing the adverse results of harsh parenting. This objective and neutral perspective can help adolescents reduce painful experiences generated by the resource loss spiral [62,63], and thus reduce the possibility of suicidal ideation.

Second, mindfulness can help adolescents detach themselves from negative experiences [15], and this detachment can reduce rumination and help relieve distressing experiences caused by harsh parenting, which can lower suicidal ideation.

As mentioned above, depressive symptoms may mediate the relationship between harsh parenting and suicidal ideation (Hypothesis 1), and mindfulness is likely to moderate the effects of harsh parenting on depressive symptoms (Hypothesis 2) and suicidal ideation (Hypothesis 3). In combination with these hypotheses, we further propose an integrated first-stage moderated mediated model, in which the indirect effect of harsh parenting on suicidal ideation via depressive symptoms would vary depending on adolescents’ levels of mindfulness. Mindfulness may buffer the indirect effect of harsh parenting on suicidal ideation by reducing automaticity and regulating negative emotions generated by the family stressor.