While depression is often characterized as a mental health disorder, research suggests depression can also affect the cognitive aspects of brain health (Wang et al., 2023). It’s likely too simplistic to say that depression affects either psychological or physiological health alone, as the cognitive symptoms of depression suggest a more complex connection between depression and the brain.
Although cognitive impairment has been shown to be associated with depression, a clinical depression diagnosis encompasses a broad range of cognitive, emotional, mental, and physical symptoms (National Institute of Mental Health [NIMH]).
This creates an opportunity for better whole person care. Depression has long been diagnosed using tools such as clinical interviews, but cognitive assessments can now supplement these measures by providing insight into the relationship between depressive disorders and cognitive impairment, aiding in diagnosis, and tracking treatment efficacy.
In this article, we discuss the cognitive symptoms of depression, their relation to brain function, and how depression impacts cognitive function.
What is Depression?
Depression is a common mental health condition marked by persistent feelings of sadness, hopelessness, and disinterest in activities—all of which have the potential to negatively impact a patient's quality of life (World Health Organization [WHO], 2025; Fernandes, M., et al., 2023). While its symptoms are often linked to emotional and mental health, depression can affect other areas of well-being, too. In some cases, depressive disorders can alter physical health, leading to extreme fatigue, or it may influence cognitive abilities like memory and attention (Kraft et al., 2023).
An estimated 29% of US adults have had a depression diagnosis at some point in their lives, according to a 2023 survey (American Psychiatry Association [APA]). And according to the National Institute of Mental Health, an estimated 21 million adults in the United States experienced a major depressive episode in 2021.
While sometimes used interchangeably with major depressive disorder (MDD), a major depressive episode is defined as a period of at least two weeks where a noticeable and substantial shift in mood occurs.
There are actually several types of depression (APA) and mood disorders that include depressed mood as a symptom:
Major Depressive Disorder (MDD)
Also known as clinical depression, MDD symptoms include a persistent feeling of sadness, a lack of interest in activities, changes in appetite, sleep disturbances, and difficulty concentrating.
Bipolar Disorder
This mental health disorder is characterized by mood changes that cycle between severe highs (mania) and lows (depression), with periods of neutral mood as well.
Perinatal or Postpartum Depression
This type of depression occurs in up to 15% of women after childbirth (Cleveland Clinic). Symptoms include extreme sadness, anxiety, and exhaustion that may interfere with daily care activities.
Persistent Depressive Disorder (Dysthymia)
Persistent depressive disorder (PDD) is a long-term, chronic form of depression. In young people, symptoms must persist for one year or more to be characterized as PDD. While effects on work, relationships and daily life can vary widely, symptoms can be equal to or great than than those of major depressive disorder.
Seasonal Affective Disorder (SAD)
This type of depression is related to changes in seasons, typically beginning during the winter months when there's less natural sunlight.
Premenstrual Dysphoric Disorder (PMDD)
This is a severe extension of premenstrual syndrome (PMS). It is associated with many symptoms including mood shifts which may resemble depression and can affect work and relationships. Other symptoms include irritability, anger, marked anxiety or tension, decreased interest, difficulty concentrating, lack of energy, changes in appetite, difficulty sleeping, joint or muscle pain, and more.
What are the Cognitive Symptoms of Depression?
While there are many symptoms of depressive disorder (WHO), several are specifically related to cognitive ability (Shilyansky et al., 2016, Eraydin et al., 2018; Kraft et al., 2023).
Cognitive symptoms of depression can include deficits in objective measures of:
- Attention
- Concentration
- Response inhibition
- Verbal memory
- Information processing
- Executive functioning
- Spatial working memory
Research on the relationship between the age of onset of a depressive disorder and cognitive function found that these cognitive impairments are also bidirectional—meaning that impairment can result from the disorder, but also may predict future depression (Eraydin et al., 2018). Individuals with depression may experience few symptoms or a wide range, depending on the person and the severity of their condition.
The Cognitive Characteristics of Depression
Physical changes in the brain may be difficult to uncover and typically aren’t observable when diagnosing or treating depression without brain imaging.
However, changes in memory, focus, and attention are all changes in cognitive functions that may provide insight into neurological shifts. These cognitive symptoms can be accurately captured via less invasive, more convenient methods such as computerized cognitive testing.
Memory
Depressed patients often experience difficulties with memory processes. One study using Creyos found that depression was related to lower performance on tests of episodic memory, working memory, and verbal short term memory (Desai, R., et al., 2020).
Patients may present with concerns including:
- Forgetfulness
- Difficulty recalling details
- Struggles with memory consolidation
These experiences can further amplify the challenges faced during a depressive episode.
Focus and Attention
An inability to focus is a common symptom of depression, which is sometimes associated with feelings of “brain fog” that may be a sign of impairment in cognitive functioning (Keller, A.S., et al., 2019). Specific impairment in attention and response inhibition resulting from depression can be measured with assessments including the Stroop test and is associated with lower performance scores (Kertzman et al., 2010).
Individuals may struggle with concentrating on tasks, response inhibition, making decisions, decision speed, or remembering details (Shilyansky et al., 2016). Difficulties with attention that are characteristic of depression can lead to challenges in both professional and personal settings, further exacerbating the distress caused by the depressive state.
How Depression Can Affect Mental Health and Emotion
Motivation
Depression can significantly impact motivation, a function crucial for initiating and maintaining goal-oriented behavior (Grahek et al., 2019). Individuals with depression often experience a marked decrease in motivation, which can manifest as a loss of interest in activities they once enjoyed, difficulty in starting tasks, or a general feeling of apathy.
Anxiety
Anxiety and depression often coexist (Millan et al., 2012; ter Meulen et al., 2021). Anxiety disorders are marked by excessive worry and fear about everyday situations. Both conditions can significantly interfere with an individual's quality of life, and they often share common symptoms such as difficulty concentrating, sleep disturbances, and changes in appetite.
Negative Emotional Bias
Negative emotional bias, a common characteristic of depression, refers to the tendency of those affected to interpret emotional stimuli and information negatively. This bias persists across various circumstances and even during remitted states of depression. It can reinforce an individual’s depressive symptoms as well as affect a person’s perception of events and self esteem.
Depression and Sleep Disruption
Sleep Disruption
One of the common symptoms of depression is insomnia. Almost three-quarters of depressed individuals experience disrupted sleep (Nutt et al., 2008). This lack of sleep may contribute to a more pessimistic mood and outlook, potentially exacerbating additional depressive symptoms.
Excessive sleepiness, also known as hypersomnia, was reported in approximately 13.7% of patients diagnosed with depression, according to a study in the Journal of Affective Disorders. This condition is characterized by prolonged night sleep, difficulty waking up, and frequent, often uncontrollable, daytime sleepiness.
Hypersomnia in depression is not just about sleeping for long hours but also about the quality of sleep. Despite spending excessive time sleeping, individuals with hypersomnia often report feeling unrefreshed or groggy upon waking. This symptom can further exacerbate feelings of fatigue and lack of energy, which are common in those suffering from depression.
What Happens to the Brain During Depression?
Research has demonstrated that the brain may change in terms of its structure and function as a result of persistent depression (Zhang et al., 2018). While these changes are only observable through brain imaging techniques, physicians can potentially recognize neurological alterations based on a patient’s cognitive or behavioral symptoms documented via cognitive assessments.
Physiological changes in brain anatomy (Oakes et al., 2016) from depression tend to occur primarily in the areas responsible for regulating emotions and stress hormones—namely, the prefrontal cortex, hippocampus, and amygdala (Pizzagalli & Roberts, 2021; Sheline 2013; Šimić et al., 2021).
Brain imaging techniques such as structural and functional magnetic resonance imaging (MRI and fMRI) have been used in research to identify specific patterns of brain activity and detect structural and functional abnormalities associated with depression (Zhang et al., 2018; Wang L. et al., 2012).
These objective findings may correspond to more subjective changes in cognition that manifest as various symptoms—from delayed memory ability to difficulty concentrating. Taking results from objective and subjective measures together is crucial to gain a complete understanding of how depression affects the brain.
While diagnosing psychiatric conditions, access to advanced MRI and fMRI tools may be expensive and difficult to obtain. At the same time, traditional cognitive screeners tend to only be accurate enough to detect the presence of cognitive decline, but lack the sensitivity to support an association between cognitive symptoms and depression.
This creates a gap in cognitive care planning which can potentially lead to less effective treatments and lower patient quality of life.
How Do Clinicians Evaluate Depression and its Effects on Cognition?
Emotional and psychological impacts are often the focus of treatments for depression. However, as cognitive deficits are researched more in depth, it’s clearer than ever that focusing on addressing and restoring cognitive health is key to depression treatment.
While subjective measures—clinical interviews, mental health and behavioral health questionnaires, and screeners—are typically used and readily available, objective tools like MRI scans and detailed neuropsychological exams may be inaccessible or unfavourable for some patients. However, without objective assessment, clinicians may have an incomplete picture of a patient's condition, possibly leading to inaccurate diagnoses and less efficient treatment plans.
Creyos Health provides a suite of cognitive tasks and psychological questionnaires that help clinicians objectively assess the neuropsychological symptoms of depression. By closing the gap between subjective and objective measures, physicians can capture patients' self-reported experiences and actual performance on standardized tests, which can provide detailed, data-driven insight and lead to a more comprehensive understanding of cognitive function and its relationship with depression.
Below we’ll expand on a few of these key methods for evaluating depression.
Cognitive Assessment
Computerized cognitive assessments can complement subjective measures like interviews and self-report questionnaires with objective data, providing a comprehensive understanding of the patient’s cognitive function. These methods are excellent for quantifying and tracking the severity of cognitive impairment in a patient, while also improving accessibility.
Cognitive healthcare solutions can help providers better understand their patients’ experiences, tailor treatment and preventative care strategies, and monitor progress over time. They can also support patients in understanding their condition and feeling empowered in managing their depression symptoms.
With Creyos computerized cognitive tests, physicians can administer regular assessment protocols throughout the care process, gathering longitudinal objective data over a period of time to inform treatment decisions and monitor cognitive abilities in the context of depression treatment. Additionally, patients are provided with a faster, more convenient solution that can be completed from the comfort of their own home—eliminating the need to jump from clinical interviews to stressful, lengthy neuropsychological testing.
To the extent that depression manifests in the brain, cognitive testing can also detect deficits that may result from differences in the brains of depressed patients without needing to immediately resort to an expensive MRI scan.
Questionnaires and Self Report
The Patient Health Questionnaire (PHQ-9) is a self-administered tool used to subjectively assess the presence and severity of depressive symptoms and monitor progress over time. Released by Pfizer in 2001, the PHQ-9 is widely utilized by various healthcare professionals as a standard method for depression screening. This questionnaire, available within Creyos Health, aids clinicians in evaluating and quantifying the severity of depressive symptoms in a patient and tracking these symptoms over time.
Other subjective measures like the General Anxiety Disorder (GAD-7) Questionnaire and the Perceived Stress Scale (PSS) can help to evaluate aspects of patient health that may be associated with depression, track treatment progress, and substantiate treatment efficacy.
Psychological Assessment and Clinical Interviews
Clinical interviews are traditionally a first step in identifying the need for further testing for depression—such as measuring cognitive and mental health, and potentially recommending further psychological support, such as therapy.
Psychotherapy plays a pivotal role in diagnosing and evaluating depression (Rogan & Wilkinson, 2023). While numerous styles of psychotherapy exist, the primary objective is to understand the patient's mental state, assess the intensity of their negative thoughts, and identify potential triggers or patterns that could indicate depression.
These subjective measures aid in a comprehensive evaluation of a patient's depressive state, offering crucial insights into the nature and severity of their condition when combined with objective data captured via cognitive assessments.
Easing the Cognitive Impacts of Depression
While major depressive disorder can significantly impact the neurology and behavior of patients, the cognitive symptoms of depression can be properly assessed, diagnosed, and managed.
Patients may find they can manage the disorder with the help of certain lifestyle changes or medical treatments, as well as careful monitoring with the tools available for a patient-centered care experience. Since depression is a complex illness, patients will need thorough follow-up and reassessment to monitor their progression and improve their overall quality of life.
Reviewed by Sydni Paleczny, Staff Scientist
Sydni earned her MSc in Neurosciences at Western University under Dr. Adrian Owen. Her research explores neuropsychological outcomes after cardiac surgery, with interests in cognitive neuroscience, critical care, and brain health. At Creyos, she supports scientific validity, health technology, and ongoing research.
Updated and reviewed: February 26, 2025