Treatment-resistant depression

Treatment-resistant depression (TRD) is a term used in clinical psychiatry to describe a condition that affects people with major depressive disorder (MDD) who do not respond adequately to a course of appropriate antidepressant medication within a certain time. Typical definitions of TRD vary, and they do not include a resistance to psychological therapies. Inadequate response has traditionally been defined as no clinical response whatsoever (e.g. no improvement in depressive symptoms). However, many clinicians consider a response inadequate if the person does not achieve full remission of symptoms. People with treatment-resistant depression who do not adequately respond to antidepressant treatment are sometimes referred to as pseudoresistant. Some factors that contribute to inadequate treatment are: early discontinuation of treatment, insufficient dosage of medication, patient noncompliance, misdiagnosis, and concurrent psychiatric disorders. Cases of treatment-resistant depression may also be referred to by which medications people with TRD are resistant to (e.g.: SSRI-resistant). In TRD adding further treatments such as psychotherapy, lithium, or aripiprazole is weakly supported as of 2019. Treatment-resistant depression (TRD) is a term used in clinical psychiatry to describe a condition that affects people with major depressive disorder (MDD) who do not respond adequately to a course of appropriate antidepressant medication within a certain time. Typical definitions of TRD vary, and they do not include a resistance to psychological therapies. Inadequate response has traditionally been defined as no clinical response whatsoever (e.g. no improvement in depressive symptoms). However, many clinicians consider a response inadequate if the person does not achieve full remission of symptoms. People with treatment-resistant depression who do not adequately respond to antidepressant treatment are sometimes referred to as pseudoresistant. Some factors that contribute to inadequate treatment are: early discontinuation of treatment, insufficient dosage of medication, patient noncompliance, misdiagnosis, and concurrent psychiatric disorders. Cases of treatment-resistant depression may also be referred to by which medications people with TRD are resistant to (e.g.: SSRI-resistant). In TRD adding further treatments such as psychotherapy, lithium, or aripiprazole is weakly supported as of 2019. Comorbid psychiatric disorders commonly go undetected in the treatment of depression. If left untreated, the symptoms of these disorders can interfere with both evaluation and treatment. Anxiety disorders are one of the most common disorder types associated with treatment-resistant depression. The two disorders commonly co-exist, and have some similar symptoms. Some studies have shown that patients with both MDD and panic disorder are the most likely to be nonresponsive to treatment. Substance abuse may also be a predictor of treatment-resistant depression. It may cause depressed patients to be noncompliant in their treatment, and the effects of certain substances can worsen the effects of depression. Other psychiatric disorders that may predict treatment-resistant depression include personality disorders, obsessive compulsive disorder, and eating disorders. Some people who are diagnosed with treatment-resistant depression may have an underlying undiagnosed health condition that is causing or contributing to their depression. Endocrine disorders like hypothyroidism, Cushing's disease, and Addison's disease are among the most commonly identified as contributing to depression. Others include diabetes, coronary artery disease, cancer, HIV, and Parkinson's disease. Another factor is that medications used to treat comorbid medical disorders may lessen the effectiveness of antidepressants or cause depression symptoms. People with depression who also display psychotic symptoms such as delusions or hallucinations are more likely to be treatment resistant. Another depressive feature that has been associated with poor response to treatment is longer duration of depressive episodes. Finally, people with more severe depression and those who are suicidal are more likely to be nonresponsive to antidepressant treatment. There are three basic categories of drug treatment that can be used when a medication course is found to be ineffective. One option is to switch the patient to a different medication. Another option is to add a medication to the patient’s current treatment. This can include combination therapy: the combination of two different types of antidepressants, or augmentation therapy: the addition of a non-antidepressant medication that may increase the effectiveness of the antidepressant. Increasing the dosage of an antidepressant is a common strategy to treat depression that does not respond after adequate treatment duration. Practitioners who use this strategy will usually increase the dose until the person reports intolerable side effects, symptoms are eliminated, or the dose is increased to the limit of what is considered safe. Studies have shown a wide variability in the effectiveness of switching antidepressants, with anywhere from 25–70% of people responding to a different antidepressant. There is support for the effectiveness of switching people to a different SSRI; 50% of people that were nonresponsive after taking one SSRI were responsive after taking a second type. Switching people with TRD to a different class of antidepressants may also be effective. People who are nonresponsive after taking an SSRI may respond to a tricyclic antidepressant, bupropion or an MAOI. However, the more antidepressants an individual had already tried, the less likely they were to benefit from a new antidepressant trial. Medications that have been shown to be effective in people with treatment-resistant depression include lithium, triiodothyronine, benzodiazepines, atypical antipsychotics, and stimulants. Adding lithium may be effective for people taking some types of antidepressants, it does not appear to be effective in patients taking SSRIs. Triiodothyroxine (T3) is a type of thyroid hormone and has been associated with improvement in mood and depression symptoms. Benzodiazepines may improve treatment-resistant depression by decreasing the adverse side effects caused by some antidepressants and therefore increasing patient compliance. Since the entry of olanzapine into psychopharmacology, many psychiatrists have been adding low dose olanzapine to antidepressants and other atypical antipsychotics such as aripiprazole and quetiapine. Eli Lilly, the company that sells both olanzapine and fluoxetine individually, has also released a combo formulation which contains olanzapine and fluoxetine in a single capsule.