Two Key Studies of Biol Treatments of Major Depressive Disorder & Phobias (HL IB Psychology)

Kroenke et al. (2001)

Key study one (a biological treatment for MDD): Kroenke et al. (2001)

Aim: To compare the effectiveness of three SSRIs (paroxetine, fluoxetine and sertraline) in treating MDD, using a large-scale randomised clinical trial.

Participants: 

• 573 patients with MDD from 37 clinics across the USA

• The participants were aged 19-96 years old (mean age=46 years) 

• 79% of the sample were female; 21% were male

• The ethnic distribution of the sample was 84% Caucasian, 13% Black and 3% other

• Each patient had been recommended for the study by their main clinician on the basis of their suitability for treatment with SSRI antidepressants 

Procedure: 

• The participants completed a baseline assessment over the telephone and were randomly assigned treatment via one of the SSRIs (189 were given paroxetine; 193 were given fluoxetine; 191 were given sertraline) for a period of 9 months

• At intervals of 1, 3, 6 and 9 months each participant completed a 36 item Mental Component Summary Score (MCSS) health scale with standardised questions designed to measure symptoms of MDD

• The participants also completed self-reports on multiple measures of other variables (which were designed to be used in conjunction with the MCSS data), for example, social and work functioning, physical functioning, sleep, memory and pain

Results:  

• 79% of participants completed the full 9 month treatment programme

• All participants improved similarly, by a mean of between 15 and 17 points on the MCSS

• All of the participants saw an improvement in depressive symptoms from 74% at baseline to 32% at 3 months and 26% at 9 months

Conclusion: 

• SSRIs may be an effective treatment for MDD

• The SSRIs paroxetine, fluoxetine and sertraline appear to be similar in their effectiveness for the treatment of MDD

Evaluation of Kroenke et al. (2001)

Strengths

• Triangulation of data was implemented via the use of several different measures e.g. MDD symptoms, social functioning, sleep which increases the reliability of the findings 

• The wide age range of the sample highlights the universal efficacy of SSRIs which increases the external validity of the findings

Limitations

• It is possible that some of the participants succumbed to the placebo effect i.e. their depressive symptoms improved because they believed that the drug they were taking would work i.e. a psychological rather than a biological explanation of their improvement

• As the participants were left to take their medication at home it is possible that not all of the participants adhered to this medical regimen which would mean that their MDD improved for other reasons: if so this would reduce the validity of the findings

Large-scale randomised clinical trials can show the efficacy of specific drugs

Liebowitz et al. (1998)

Key study two (a biological treatment for phobias): Liebowitz et al. (1998)

Aim: To investigate the effectiveness of the MAOI phenelzine as a treatment for social phobia

Participants: 80 patients aged 18-50 years old who had been diagnosed with social phobia. 

Procedure: 

• A lab experiment with an independent measures design: each participant was randomly assigned to one of four groups:

  • Phenelzine treatment group

  •  Placebo for phenelzine group

  • Atenolol treatment group (atenolol is a beta blocker drug used to treat hypertension)

  •  Placebo for atenolol group

• The participants were given increasing doses of either phenelzine or atenolol or the placebo over the course of 8 weeks

• After the 8 week trial period was over the participants were assessed using the Hamilton Rating Scale for Anxiety and the Liebowitz Social Phobia Scale

• The Hamilton Rating Scale for Anxiety measures the severity of anxiety symptoms on a scale of 0 to 4 (4=severe)

• The Liebowitz Social Phobia Scale  assesses the way that social anxiety plays a role in a variety of situations e.g. attending a party, eating in public, public speaking, measured on a scale of 0-3 (3=severe) and 0-3 (3=usually)

Results: 

• The participants in the phenelzine treatment group had improved scores for anxiety compared to the placebo groups i.e. their social phobia had decreased over the course of the 8-week trial

• There was no significant difference seen in the atenolol group when compared to the placebo group i.e. atenolol does not appear to improve social phobia

Conclusion:  Phenelzine appears to be an effective treatment for social phobia.

Evaluation of Leibowitz et al. (1988)

Strengths

• Independent assessors who were blind to the condition each participant was in i.e. drug or placebo, conducted the clinical assessments which increases the validity of the findings as it eliminates bias

• The findings support the idea that phobias should be treated with medication other than SSRIs as the symptoms are more in line with anxiety disorders than depressive disorders

Limitations

• A sample of 80 participants divided across 4 conditions means that the number of participants per condition is likely to be 20 which decreases reliability due to the reduced statistical power of the sample size.

• An independent measures design runs the risk of individual differences affecting the results i.e. some of the participants may simply have more resilience than others and thus be able to deal with their phobias more successfully than others 

Key terms: MAOI  Beta-blocker  Social phobia