Major Depressive Disorder vs Persistent Depressive Disorder (Dysthymia)

Mood refers to a persistent and long-lasting feeling that a person experiences internally. It impacts the overall behaviour of an individual. Mood disorders are also known as affective disorders. One of the most essential features of mood disorders is changes in the level of emotions, which means they are marked by relative disruption in emotional levels.

The two distinguishing features are: Mania (excessive or more than usual level of excitement leading to manic episodes), hypomania(relatively less excitement than mania but there is presence of elevated mood) and depressive episodes(includes the feelings of sadness, hopelessness, unworthiness, etc.). These are common psychiatric disorders and are largely prevalent in males and females both.

Mood disorders impair the regular functioning of an individual’s health; they impact their sleep, routine, and physiological functioning. The DSM -5 and ICD – 11 further classify mood disorders as Bipolar disorders, which consist of Bipolar I & II , Cyclothemia, Depressive Disorders include Major Depressive Disorder, Persistent Depressive Disorder (Dysthymia). This article aims to understand depression, dysthymia, , are they similar or different, causes, meaning and criteria of each(Sekhon et al., 2023; America Psychiatric Association,2013). 

Major Depressive Disorder (MDD)

In earlier times, mood disorders were categorised under depressive disorders, affective disorders, or depressive neuroses. With the coming of the third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III), published by the American Psychiatric Disorder in 1980, these were grouped under mood disorders. The most severely described depression is known as a Major Depressive Episode.

The DSM-5 criteria describe it as an extremely depressed mood state for at least two weeks. It includes vegetative, cognitive, and physical symptoms. Major depressive episodes are also marked by loss of interest in day-to-day life. One of the central indicators of MDD is vegetative symptoms. Women are diagnosed more often than men, but men are also diagnosed with depression. Depression can co-occur with chronic illness such as diabetes, cancer, and heart disease.

Depression impacts them, and vice versa. The two common types of depression are major depression and persistent depressive disorder, which is also known as dysthymia. According to estimates, in 2019, 280 million people experienced depression. It is estimated that 12 billion productive days are lost every year to depression and anxiety. Major depressive disorder is associated with a high mortality rate, which is caused by suicide. 

Onset

It may start at a certain age. There is no specific age criterion. The course of depression varies from individual to individual. Some of them experience an episode with some or few symptoms, whereas some might experience it continuously. The risk is higher in individuals whose earlier episodes were severe. Features associated with lower recovery rates are psychotic features, anxiety, and personality disorders. 

Causes and Treatment

There are multiple causes of depression; it is not caused by only one factor. Family Studies suggest that individuals with a family history of major depression are more prone to develop it. According to Beck, individuals with depression have a negative thinking style and have cognitive distortions. Their usual way of thinking is negative, which leads to more severe symptoms.

They either sleep more than usual or sleep less than usual. Individuals with depression have dysregulated sleep and circadian rhythm. There are also significant changes in the neurotransmitter system, especially dopamine. Stress reduces the secretion of dopamine and produces depressive – like behaviour. Learned helplessness is another cause of depression. Individuals with depression feel helpless, and they project it to their outer world as well.

It also involves complex changes in the endocrine system, nervous system, brain circuitry, etc.  Treatment intervention involves both psychopharmacological treatment and therapy. Best results are derived when both are used by the clinicians. Psychopharmacological treatment includes the prescription of Antidepressants and Mood stabilizers. Four types of antidepressants include: SSRIs, Mixed Reuptake Inhibitors, Tricyclic Antidepressants, and monoamine oxidase inhibitors. 

• SSRIs: They specifically block the presynaptic reuptake of serotonin; this enables serotonin to be there at the receptor site. There are prominent side effects of SSRIs such as : Nausea, Diarrhea, Insomnia, Sexual Dysfunction, Agitation ect. 
• Monoamine Oxidase Inhibitors (MAOIs): They work by blocking the MAO enzymes. MAO enzymes break the neurotransmitter such as : Serotonin and Norepinephrine. These neurotransmitters play a vital role in mood regulation. 
• Tricyclic Antidepressants: These were mostly prescribed and used before the introduction of SSRIs, yet it is not known how they work, although they block the reuptake of certain neurotransmitters. Prominent side effects are blurred vision, dry mouth, difficulty urinating, drowsiness, etc. 
• Electroconvulsive Therapy (ECT) : It was introduced in the 20th century, earlier it used to be harmful but ECT today has changed and is beneficial in severe cases. In current cases, patients are first given anaesthesia to reduce uneasiness and increase relaxation. An electric shock is delivered to the brain for less than a second. This produces seizures and electric convulsions that last for several minutes. 
• Cognitive Behavioural Therapy: CBT focuses on altering the negative thoughts of clients. Through cognitive restructuring, therapists teach clients to understand how their negative and distorted thinking affects them. CBT is structured and well-planned, which helps clients understand their cognition. Research shows that CBT is effective and produces remarkable changes in clients.
• Interpersonal Psychotherapy: It prominently focuses on the existing problems within interpersonal relationships. The therapist and client together work on interpersonal problems. It progresses through three stages: Negotiation, Impasses, Resolution Stage (Barlow & Durand, 2015; American Psychiatric Association, 2013; National Institute of Mental Health, 2024; World Health Organisation, n.d.). 

Persistent Depressive Disorders (Dysthymia)

Persistent Depressive Disorder is a chronic and incapacitating (makes somebody unable to do something) form of depression. It affects 3-6% of the population in general. This has been controversial over the years because some regard it as a mood disorder while some regard it as a personality disorder. According to the DSM-5, Persistent Depressive Disorder (PDD), also known as Dysthymia, is a chronic form of depression. It involves a depressed mood that lasts for most of the day, on more days than not, for at least two years in adults. In children and adolescents, it must last for at least one year.

The patient experienced a low level of symptoms. It manifests as withdrawal from daily routine and avoiding it rather than facing it. One of the major issues is that Clinicians may fail to recognise these patients, and the majority exhibit comorbidity with other disorders. The aetiology of Dysthymia is as complex as that of depression. All factors play a role, such as biopsychosocial factors. The diagnosis of Persistent Depressive Disorder is not straightforward. Clinicians also called it Neurotic Disorder. The DSM-III introduced the diagnosis in 1980.

Clinicians diagnose Dysthymia when an individual experiences depressive symptoms for more than two years. The symptoms must not include a major depressive episode or a manic episode. If an individual experiences an episode of major depression or mania, clinicians may diagnose them with Major Depressive Disorder or Bipolar Disorder (I or II), depending on their symptoms. The important features of Dysthymia are that there should not be a complete episode of depression, and it should persist for up to 2 years.  Dysthymia is chronic in nature and causes significant impact on day-to-day functioning.

Individuals with comorbidity of personality disorders experience severe pain. It is estimated that individuals with Dysthymia have a risk of 71. 4% of relapsing into depression. What makes Dysthymia severe and chronic is that individuals with Dysthymia are more prone to attempt suicide than those with depression. The aetiology is similar to that of major depression. Possible causes of Dysthymia include lack of sleep, circadian rhythm, serotonin dysregulation, etc. Females who experience Dysthymia have a history of thyroid dysfunction. 

Cornell Dysthymia Rating Scale

The Cornell Dysthymia Rating Scale was first developed in 1993 by Mason and colleagues; since its development, it has been an efficient tool for screening. The CDRS is a simple scale with a 20-item questionnaire. It specifically assesses the symptoms and severity of Dysthymia over the week. Each item receives a score between 0 and 4. The total score ranges from 0 to 80. Higher scores indicate greater severity of symptoms.

While the CDRS is great for spotting potential issues and tracking progress, it is important to remember that screening tools are not the same as official diagnoses. A screening tool like the CDRS simply flags whether someone might have a problem. A real diagnosis, on the other hand, requires a full evaluation by a trained mental health professional using standard diagnostic manuals (like the DSM or ICD). Therefore, clinicians should use the CDRS only to screen for and monitor symptoms. It should never replace an official medical diagnosis.

Treatment

Considering the treatment for dysthymia, it is similar to that of depression. Clinicians often combine antidepressant medication with psychotherapy when treating patients (Spanemberg, 2004; Melrose, 2017).

Are they similar? 

Although Major Depressive Disorder and Persistent Depressive Disorder come under the same category of depressive disorders, they are not similar in nature. Clinicians and students often find this distinction confusing. The DSM diagnostic criteria can help clarify the differences.

1. Major Depressive Disorder (MDD)

The diagnostic criteria for MDD suggest that five or more symptoms should be present in the same two-week period, and at least one of the symptoms is: 1. Depressed Mood and 2. Loss of interest or pleasure. 

Symptoms of MDD

Depressed Mood most for most of the days, Lack of interest or pleasure in most of the activities, weight loss, insomnia and hypersomnia, psychomotor agitation, fatigue, feelings of worthlessness, inability to think or concentrate, recurrent thoughts of death and suicidal ideation.  At least one major depressive episode must occur without being attributable to schizoaffective disorder.

2. Persistent Depressive Disorder or Dysthymia

The criteria for PDD suggests that there should be a depressed mood for most of the days and at least for 2 years for adults. 

Symptoms of PDD

Poor Appetite, Overeating, Insomnia, Hypersomnia, Fatigue and low self-esteem, poor concentration and a feeling of hopelessness.  During the entire period, the individual should have experienced the above conditions.  Criteria for MDD should be present continuously for 2 years. There has never been a manic or hypomanic episode. If an individual experiences a manic or hypomanic episode, clinicians may diagnose them with Bipolar I or Bipolar II Disorder, respectively (American Psychiatric Association, 2013).

The difference 

1. Major Depressive Disorder (MDD) involves one or more major depressive episodes. In contrast, Persistent Depressive Disorder (PDD) involves a long-lasting depressed mood, which may also include major depressive episodes.  
2. For MDD, the symptoms should be present for 2 weeks, and for PDD, the symptoms should be present at least for 2 years. 
3. The symptoms of MDD are intense and severe, whereas the symptoms of PDD are less intense but last longer than MDD. 
4. The course of MDD manifests as one or more episodes with periods of recovery, and for PDD the symptoms are Persistent with no symptom-free period for more than 2 months. 

Case Snippet

Identify which case is of MDD and PDD. As a clinician, what screening tool would you make use of to rule out comorbidity? 

1. A college-going student experiences sadness, loss of interest, fatigue, feelings of hopelessness, and sleep disturbances for three weeks. These symptoms are significantly interfering with day-to-day life. 
2. An employee experiences low mood, low self-esteem, and hopelessness for three years. Although he goes to work, he frequently feels unhappy and worthless.  

Conclusion

Major Depressive Disorder and Persistent Depressive Disorder are classified as depressive disorders. Depressive disorders are classified as mood disorders. MDD and PDD differ from each other in terms of duration, course, and severity of symptoms. The symptoms remain the same in both but differ in the above aspects. A Clinician should make use of screening tools in order to avoid misdiagnosis of disorders. Over 51% of patients often go undiagnosed.