1. Introduction

Depression is a prevalent mental health disorder that significantly diminishes the quality of life for millions worldwide. The World Health Organization indicates a sustained increase in its prevalence, establishing it as a critical public health challenge. A range of treatment approaches are available for depression, with cognitive behavioral therapy (CBT) and psychodynamic therapy being two of the most commonly used. Each of these therapies has its own theoretical foundation and treatment mechanisms. Despite numerous studies comparing their effectiveness, there remains a significant gap in research on their underlying mechanisms of action. Thus, a deeper understanding of the factors that contribute to the effectiveness of these two therapies is essential for creating more targeted treatment strategies. The paper aims to analyze the effective factors of psychodynamic therapy and cognitive-behavioral therapy in the treatment of depression, and to propose individualized treatment recommendations based on the individual differences of depressed patients. As such, it reviews the relevant literature, concentrating on face-to-face individual therapy while excluding studies on group and online therapy. In addition, meta-analyses and case studies were reviewed to compare the efficacy of the two therapies. Studies that do not include Randomized-Controlled Trials (RCT) are excluded to ensure the rigor and reliability of the findings. By comparing different treatments, this paper aims to provide empirical support for personalized depression treatment and also highlights the limitations of existing studies to promote further development in the field of depression treatment.

2. Major Causes of Depression

Depression arises from multiple theoretical perspectives, including intrapsychic conflict, cognitive-behavioral models, and negative feedback loops, each offering distinct insights into its complexity. Inner conflict often arises from a strong desire for interpersonal connection, perceptions of rejection and dislike, and feelings of helplessness and disappointment, all linked to deficits in self-functioning. [1]. Psychoanalytic theory highlights that the “poverty and emptiness” of the ego state is central to depression, leading to a significant denial of self-worth that worsens the condition [2]. In contrast, CBT introduces the concept of “depression interlock,” which posits that automatic thoughts and images related to triggering situational memories activate depressive moods. This cognitive pattern influences emotional states while also shaping the individual’s thought processes and responses to reality, thus perpetuating a cycle of depressive symptoms [3]. Moreover, the theory of the negative feedback loop further elucidates the self-reinforcing mechanism of depressive symptoms: the negative feelings that individuals with depression experience regarding their condition can establish a self-perpetuating cycle, making it difficult for them to break free from their depressive state. Over time, this cycle deepens depressive symptoms and may also result in the patient’s resistance to treatment, further obstructing the recovery process [4]. Thus, the upcoming discussion will analyze the methodologies and theoretical frameworks of psychodynamic therapy and CBT, focusing on intervening in deep-seated inner conflicts and cognitive biases. And this approach aims to help patients rebuild their self-worth and enhance their emotional regulation skills. These theories provide a crucial framework for understanding the causes of depression and establish a foundation for effective treatment strategies, emphasizing the inner conflicts and cognitive challenges that individuals must confront and resolve in the therapeutic process.

3. Treatment Methods and Effectiveness Evaluation

In the treatment of depression, it is important to choose the most appropriate therapeutic approach.. Psychodynamic therapy and CBT are two widely used and uniquely characterised treatments. This section evaluates the theoretical frameworks of these two therapies and their clinical efficacy, exploring how they affect patients with depression through different mechanisms. In addition, the study analyzes relevant randomized controlled trials and patient subjective experiences to provide a comprehensive understanding of the advantages and limitations of each treatment method, thereby offering a scientific basis for personalized therapy.

3.1. Psychodynamic Therapy

3.1.1. Theoretical Framework

Three models of psychodynamic approaches are proposed: the drive-structural model, the relational model, and the integrative analytic model [5]. The drive-structural model is mostly used in short-term psychodynamic psychotherapy (STPP) and intensive short-term dynamic psychotherapy (ISTDPP), aiming at surmounting unconscious defenses such as resistance [5]. Despite its intensity and potential to provoke stress, the goal of overcoming resistance is to enable patients to access their most authentic and profound feelings. The relational model, commonly utilized in psychodynamic supportive therapy and supportive expressive therapy, emphasizes addressing unhealthy early attachment styles that arise from relationships with primary caregivers [5]. This model uses the interpersonal relationship with the therapist to establish positive feelings like support, acceptance, encouragement and affection [6]. The integrative analytic model has an ultimate goal of dealing with separation and individuation [7], therefore it is time-limited and close-ended [5]. In this stage-process model, the patient progresses through three phases with the therapist: the swift surge of positive emotions, the emergence of internal conflicts regarding the therapist and the treatment process, and the development of a challenged yet strengthened relationship that guides the therapy toward completion [5,8]. The integrative analytic model combines the drive-structure/Freudian model with the relational model to encourage patients to confront ambivalence and complex emotions while emphasizing the beneficial effects of healthy relationships.

3.1.2. Effectiveness in Treating Depression

The effectiveness of psychodynamic treatment will be evaluated through two main lenses: quantitative effectiveness derived from multiple RCTs and qualitative insights reflecting the subjective experiences of patients. This dual approach allows for a comprehensive understanding of psychodynamic therapy's impact, highlighting not only the measurable outcomes in symptom reduction but also the personal narratives that illustrate how patients perceive and experience their therapeutic journey.

Mata-analysis comparing the effect of STPP, waitlist control groups and care as usual groups has found that STPP yields a significant post-treatment effect size [9]. The pre- to post- treatment effect sizes when Back Depression Inventory (BDI) and Hamilton Depression Rating Scale (HAMD) are outcome measures are both significant for STPP [9]. In follow-up studies, depression level change shows a non-significant increase 1 year after STPP treatment [9]. Within the general categories of psychodynamic therapies, the supportive mode which bases on the relational model and the expressive mode which deals with core conflicts in depression discussed above [1] resulted in similar pre- and post-treatment effect sizes [9]. Other hindering factors such as therapist training, number of sessions and use of antidepressants did not cause much difference in mean effect sizes [9].

The subjective reports of patients show that the intended influence of psychodynamic treatment can be received. Patients have reported learning to actively choose to open up, gradually building trust with the therapist [10]. This aligns with the relational model, which suggests that relational-oriented approaches foster positive experiences. Patients have also faced seemingly aversive feelings, such as feeling “pressured” by therapists to focus on their inner thoughts and emotions rather than the external environment and others’ perspectives [10]. Although initially uncomfortable, the pressures ultimately resulted in greater openness and shifted thought patterns, offering patients new perspectives on their feelings [10]. The results indicate the capability of psychodynamic therapies in changing underlying schemas by identifying and interpreting unconscious beliefs and behavioral patterns. And qualitative research shows that patients actively engage in their therapy, with increased openness stemming from their intentional effort to build healthy relationships with therapists. Many reported that achievements outside therapy, such as participating in activities and sports, positively impacted their well-being, although this aligns more with cognitive-behavioral principles [10].

3.2. Cognitive Behavioral Therapy

3.2.1. Theoretical Framework

The dual representation theory posits that memory is influenced by two distinct systems: the implicit memory system and the explicit memory system. This theoretical framework underpins the cognitive-behavioral model, which asserts that human cognition operates through two systems, one that functions outside of conscious awareness and another that engages with conscious experience [3]. This model incorporates behavioral theories, thus highlighting that unconscious processing is shaped by prior experiences linked to specific stimuli, which elicits rigid, patterned responses [3]. These responses, being situationally accessible, play a crucial role in perpetuating depressive symptoms. Contemporary CBT targets both memory systems, aiming to modify the unconscious cognitive processes that contribute to depression. By disrupting the activation of ingrained, situationally accessible memories, CBT facilitates the replacement of maladaptive cognitive frameworks with healthier cognitive and behavioral self-management strategies [3]. This dual approach not only addresses immediate symptoms but also fosters long-term resilience by reshaping the cognitive landscape of the individual.

3.2.2. Effectiveness in Treating Depression

Most studies in this review on the effect of CBT on depression include interventions that fit into the CBT spectrum because more detailed definition of CBT intervention currently remains limited. CBT was found to be effective in treating depression both in clinical settings and in controlled experimental conditions [10-12]. Compared with core CBT techniques alone (mainly applying behavioral activation and cognitive restructuring), incorporating core CBT with other treatment components exerted more alleviation of depression symptoms [11,12]. Specifically, combining CBT with relaxation techniques (such as mindfulness), problem-coping skills, psychoeducation, self-management abilities and prevention of recurrence of symptoms yielded persistent significance in the long term [12].

Beck and Kovacs [13] had proposed that CBT techniques working with unconscious processing such as identifying and correcting maladaptive reasoning reduce depressive symptoms both in the short term and long term. Although short-term CBT was found to be most effective in alleviating depressive symptoms in dose-response studies [14], these effects did not seem to persist to mid-term in other studies [15]. This discrepancy might be due to the difference in CBT techniques applied to the treatment groups in different studies. As proposed by Teasdale [4], treatment approaches that reduced “depression about depression” generated significant effect as rapidly as in the first three weeks of cognitive treatment, and patients with the most aversive feelings about depression showed the greatest responses to the early treatments.

4. Effectiveness Comparison and Key Findings

4.1. Validity Comparison

Results from subgroup analyses and RCTs suggest that psychodynamic therapy and CBT have similar effect sizes in terms of short-term treatment effects, with both demonstrating effectiveness. However, this conclusion should be taken with caution due to the relatively limited number of included studies. In addition, the effective moderators of CBT and its mechanisms of action have not been fully elucidated, which poses a potential challenge to the broad applicability of efficacy. An in-depth exploration of potential moderating variables affecting efficacy, such as patients’ pathologic characteristics, such as disease duration, co-morbidities, individual psychological traits, such as gender, age, socio-cultural background, as well as therapists' professionalism and therapeutic styles, would provide a more precise perspective to understand the differences in the efficacy of the two treatment modalities in different patient populations. This multidimensional analysis will not only help to improve the explanatory power of the results, but also provide a theoretical basis for the development of future individualized treatment strategies, optimizing the overall treatment outcome and long-term prognosis of patients [9].

4.2. Strengths and Limitations

Due to individual differences, people with depression should be treated appropriately. Therapists need to delve into the core conflicts and factors that lead to depression in order to suggest the most appropriate treatment. In addition, the number of planned treatments that the patient is able to accept should be considered, as psychodynamic therapy usually requires setting initial goals. This review only compares STPP and CBT in short-term psychotherapy. It is worth noting that other psychodynamic approaches show effects after a much longer period of time, and their efficacy is considered to be long-lasting because the therapeutic process occurs at a deeper level of the unconscious. Therefore, the results of the present review are mainly used to assess the effects of short-term treatments and cannot fully summarize the overall impact of psychodynamic therapies. Regarding the limitations of the study design, first, the generalizability of the results may be limited due to biases in sample selection. For example, the selection of participants in the study may not have been sufficiently representative of the broader population of people with depression, which may affect the generalizability of the treatment effects. Second, individual differences in patients may not have been adequately considered in the study design, which may lead to misinterpretation of treatment response. Therefore, it is important to be cautious when interpreting the results and to be aware that these limitations may affect the reliability of the conclusions.

5. Conclusion

This paper demonstrates that both short-term psychodynamic therapy (STPP) and short-term cognitive behavioral therapy (CBT) show significant efficacy in interventions for patients with depression, especially for those who need rapid results. This finding provides an important guideline for clinical practice. However, there are some limitations of the study. First, the small number of included studies may affect the statistical validity of the results. In addition, sample selection bias and study design limitations in selected studies were not adequately discussed, which may lead to an incomplete understanding of efficacy. This review mainly focused on STPP and CBT and failed to cover the potential benefits of other psychodynamic approaches in long-term treatment. Therefore, future studies should focus on the key factors affecting long-term efficacy in different treatment modalities, especially in the context of individual differences. It is also particularly important to analyze in depth the impact of study design limitations and sample selection on outcomes. It is recommended that larger randomized controlled trials be conducted to validate the effects of different treatments and to provide a more solid theoretical basis for individualized treatment.