Drug Therapy for Major Depressive Disorder (MDD) (DP IB Psychology): Revision Note

Drug therapy for MDD

• Biological treatments aim to treat disorders such as MDD by targeting brain chemistry

• Antidepressants are the most widely prescribed drug therapy for MDD

Types of antidepressants

• Selective Serotonin Reuptake Inhibitors (SSRIs)

  • SSRIs prevent the reuptake of serotonin into the presynaptic neuron by increasing serotonin in the synaptic cleft

  • Examples of SSRIs that are most commonly prescribed include fluoxetine and citalopram

• Serotonin-Noradrenaline Reuptake Inhibitors (SNRIs)

  • SNRIs work similarly to SSRIs but also increase noradrenaline

  • They are considered more effective for some patients

  • Examples of SNRIs include duloxetine and venlafaxine

Link to the monoamine hypothesis

• Low or irregular serotonin levels have been linked to depressive symptoms

• This supports the monoamine hypothesis, which suggests that MDD is partly due to imbalances in neurotransmitters such as serotonin

• SSRIs restore balance by keeping more serotonin available in the synapse as they prevent serotonin molecules from being absorbed back into the presynaptic neuron

Research support for drug therapy & MDD

Kroenke et al. (2001)

Aim:

• To compare the effectiveness of three SSRIs (paroxetine, fluoxetine, and sertraline) in treating MDD

Participants: 

• 573 patients with MDD from 37 clinics across the USA

• The participants were:

  • 84% Caucasian, 13% Black, 3% other

  • 79% female, 21% male aged 19–96 (mean age = 46)

  • Clinically recommended for SSRI treatment

Procedure: 

• The participants completed a baseline assessment over the telephone and were randomly assigned to one of three SSRIs (approximately 190 per group)

• Treatment lasted 9 months

• At 1, 3, 6 and 9 months, each participant completed:

  • a Mental Component Summary Score (MCSS) scale with 36 items measuring MDD symptoms

  • self-reports on social/work functioning, physical health, sleep, memory, and pain

Results:  

• 79% completed the full 9-month treatment programme

• Participants improved similarly across all three SSRIs (15–17 point improvement on MCSS)

• Depressive symptoms decreased from:

  • 74% at baseline

  • 32% at 3 months

  • 26% at 9 months

Conclusion: 

• SSRIs are effective in treating MDD

• Paroxetine, fluoxetine, and sertraline show similar levels of effectiveness

Evaluation of drug therapy & MDD

Strengths

• Reduced hospitalisation

  • Antidepressants have allowed many people with MDD to manage their symptoms outside hospital, giving patients more freedom and autonomy

• Drug therapy is generally cheap and widely available, unlike CBT which requires trained therapists, takes longer, and often involves long waiting lists

Limitations

• Although SSRIs are the most common treatment for MDD, there is a debate over their effectiveness, as some clinicians argue their effects may be little better than a placebo

• There is also uncertainty about the monoamine hypothesis, as it is likely that depression is not a single disorder with one cause but a cluster of disorders with multiple underlying biological and psychological factors

Link to concepts

Responsibility

• Drug therapy can be effective (see the above study) but it does not address the root cause(s) of MDD; it merely holds the symptoms at bay, with the possibility that MDD may recur later

• Antidepressants may have side-effects as they work directly on the brain, so the attending clinician should monitor the patient to ensure that there are no harmful consequences of taking the drug

Change

• MDD is not a stable, unchanging condition: it is subject to fluctuation and change over time

  • Life events, hormonal changes, illnesses for example, can determine the onset of MDD or, conversely, the reduction or elimination of the disorder from a person’s life

• Drugs may be a suitable therapy for MDD at one point in someone’s life but not necessarily for every time they experience depressive symptoms

  • Therefore, the whole person should be considered when prescribing treatment, rather than taking the biologically reductionist route of drug therapy for every instance of MDD