![[Adobe Stock]](https://sp-ao.shortpixel.ai/client/to_webp,q_glossy,ret_img,w_750,h_375/https://www.psypost.org/wp-content/uploads/2024/08/pills-750x375.jpg)
A commonly prescribed antidepressant may improve core emotional symptoms of depression much faster than previously thought. A new analysis reveals that while the drug sertraline offers relief from sadness and anxiety within two weeks, these benefits are often masked by simultaneous physical side effects when looking at combined symptom scores. These findings were published in Nature Mental Health.
Measuring the effectiveness of treatments for mental health conditions has historically proven difficult. Clinical trials typically rely on total scores derived from standardized questionnaires, such as the Patient Health Questionnaire or the Beck Depression Inventory.
These surveys ask patients to rate the severity of various experiences, ranging from mood and self-esteem to sleep quality and appetite. Researchers then sum these ratings to produce a single number representing the severity of the patient’s depression. This approach assumes that all symptoms are equally informative regarding the underlying condition.
However, depression is a highly heterogeneous disorder. Two individuals with the same diagnosis may share very few specific complaints. One person might struggle primarily with insomnia and agitation, while another experiences hypersomnia and lethargy. This variability complicates the assessment of how well a medication works. If a drug improves mood but simultaneously disrupts sleep or appetite, the total score might remain unchanged. This statistical canceling out can create the illusion that the medication is ineffective during the early stages of treatment.
Researchers from University College London sought to untangle these contradictory signals. They conducted a secondary analysis of data from the PANDA trial, a large randomized controlled study originally published in 2019. The original trial involved 653 adults recruited from primary care settings in the United Kingdom who were experiencing depressive symptoms. These participants were randomly assigned to receive either sertraline, a selective serotonin reuptake inhibitor, or a placebo for a period of 12 weeks.
The lead authors of the new analysis include Giulia G. Piazza and Jean-Baptiste Pingault from the Department of Clinical, Educational and Health Psychology at University College London. They collaborated with Glyn Lewis and other experts from the Division of Psychiatry. The team aimed to move beyond the limitations of total scores by employing a statistical technique known as network analysis. This method allows scientists to model individual symptoms as “nodes” and the statistical associations between them as “edges.”
By treating symptoms as individual components rather than a monolithic whole, the investigators could observe how specific aspects of mental health responded to the drug over time. They examined the direct effects of sertraline on 21 distinct symptoms at two weeks, six weeks, and 12 weeks. This granular approach enabled them to distinguish between the therapeutic benefits of the medication and its physiological side effects.
The analysis revealed that sertraline began to alleviate specific emotional symptoms much earlier than the original trial results suggested. Patients taking the medication reported reductions in feelings of sadness, self-loathing, and restlessness after just two weeks. They also experienced a decrease in suicidal thoughts compared to the placebo group. These improvements occurred well before the six-week mark, which is often cited as the typical timeframe for antidepressants to show clinical efficacy.
Despite these early emotional benefits, the drug also triggered adverse physical reactions during the same period. Patients in the sertraline group reported increased problems with libido, sleep, and appetite. Because these physical complaints are also listed as symptoms on depression questionnaires, they contributed to the total depression score. This simultaneous improvement in mood and deterioration in physical comfort effectively neutralized the overall score in the early weeks.
Giulia Piazza, the lead author, noted the importance of viewing these conditions as complex systems. She stated, “Instead of thinking of depression and anxiety as each being a single, uniform condition, network analysis considers that they’re each a constellation of symptoms, that can appear in different combinations for different people. These symptoms influence each other over time; for example, poor sleep can lead to problems with concentration, which may then impact self-esteem.”
The study found that the trajectory of these opposing effects shifted as treatment continued. While the beneficial impact on anxiety and mood persisted and deepened over the 12-week period, the negative physical side effects appeared to plateau. By the six-week mark, the adverse effects on sleep and libido had largely stabilized. This suggests that the body may adjust to the medication’s physiological impact while the psychological benefits continue to accrue.
In addition to tracking individual symptoms, the researchers investigated whether sertraline altered the relationships between symptoms. Network theory posits that symptoms can reinforce one another, creating a self-sustaining cycle of distress. For instance, anxiety might lead to insomnia, which in turn worsens anxiety. The team hypothesized that the antidepressant might work by breaking these maladaptive links.
The results indicated that the medication did not significantly change the structure of the symptom network. The associations between different symptoms remained comparable between the sertraline and placebo groups. The drug appeared to work by reducing the intensity of specific nodes within the network rather than by rewiring the connections between them. This implies that sertraline lowers the volume of specific complaints without necessarily disrupting the mechanism by which one symptom triggers another.
Professor Jean-Baptiste Pingault, co-senior author, highlighted the broader implications of this granular focus. He explained, “We found that the beneficial effects of sertraline can be detected very early on, as soon as two weeks after people start taking the antidepressant. Beyond this study, our results highlight the importance of considering symptom-level effects when developing novel drugs and evaluating existing drugs in psychiatry, and how this can help us to understand how these drugs work and how they can help patients.”
These findings provide context for why many patients may feel ambivalent about their treatment in the first few weeks. A patient might feel slightly less sad but significantly more tired or nauseous. Without clear guidance, they might conclude the medication is making them worse. Understanding that somatic side effects can temporarily mask emotional progress could help clinicians encourage adherence during the difficult initial phase of therapy.
There are limitations to this analysis that require consideration. The study was a secondary analysis, meaning the data were originally collected for a different purpose with fixed intervals for assessment. The researchers could only analyze the specific symptoms included in the original questionnaires. Some symptoms may be measured more reliably than others, potentially skewing the network map.
Additionally, the study relied on self-reported measures from patients. While this is standard in psychiatric research, subjective reporting can introduce bias. The sample was drawn from a primary care setting, which makes the findings highly relevant to general practice but perhaps less applicable to severe, treatment-resistant cases seen in specialized psychiatric facilities.
Future research will likely need to employ trial designs specifically created for network analysis. Studies that track symptoms on a daily or weekly basis could provide an even higher resolution picture of how antidepressants function. Such high-frequency data would allow researchers to see exactly when specific side effects peak and when therapeutic effects begin to dominate the clinical picture.
Atheeshaan Arumuham, an Academic Clinical Fellow at King’s College London who was not involved in the study, commented on the clinical utility of this research. He told the Science Media Centre, “For patients, this means that early treatment may feel mixed or even discouraging, not because the medication isn’t working, but because side effects temporarily overshadow progress. For clinicians and the public, it highlights the need to separate illness-related symptoms from medication-related effects when evaluating the effectiveness of antidepressant treatment.”
The study provides a more nuanced understanding of how selective serotonin reuptake inhibitors function. It challenges the binary view of treatment success or failure based on a single number. By acknowledging that a drug can simultaneously help and hinder different aspects of a patient’s experience, the medical community can offer better guidance to those navigating the complexities of mental health treatment.
The study, “The effect of sertraline on networks of mood and anxiety symptoms: secondary analysis of the PANDA randomized controlled trial,” was authored by Giulia G. Piazza, Andrea G. Allegrini, Larisa Duffy, Gemma Lewis, Glyn Lewis, Jonathan P. Roiser & Jean-Baptiste Pingault.
