Clinical - Longitudinal and cross sectional studies

What is a longitudinal study?

A study done on the same group of pp over a long period of time

What are the two clinical studies we use that use the longitudinal method?

- Carol (CBT treating S1 over 3 years, 1 year check up)

- Brown (development of depression over 1 year)

- Heston (S1 development over 35 years)

Why are longitudinal studies important in clinical?

- Studies are more holistic (not just taking one factor into account)

- Diseases develop over time e.g. S1 -ve symptoms appear first then +ve. Short term means you wouldn't see this development

- Symptoms can overlap if you don't look long term e.g. -ve S1 symptoms can look like depression

What are some issues with longitudinal studies?

- Drop out rates (people with worse experiences may drop out more so study less reflective) (attrition)

- Diagnoses can change e.g. initial depression diagnosis can change to S1 even if person is part of depression study

- Cohort effects

- Very expensive compared to cross-sectional studies (have to analyse lots of data over long time so need people - payments)

What are cohort effects?

Influences associated with growing up at a particular time/through a particular event that affect people of a particular age. This can make it hard to generalise events to those who have different life experiences e.g. COVID

(affects sample which then affects generalisability

How does the cohort effect affect longitudinal studies?

Pp will have been diagnosed using different criteria depending on which diagnostic manual was used to assess their disorder. This can make it hard to generalise findings from certain past groups to current groups

What type of study can mitigate some of the weaknesses of longitudinal studies?

Cross-sectional studies

What weaknesses of longitudinal studies do cross sectional not have?

Expensive and time consuming

What are cross-sectional studies?

They look at two groups of pp at one moment in time and compare e.g. compare 3 year olds and 5 year olds and compare rather than following 3 year olds for 2 years

How many times are pp tested in cross-sectional studies?

Once (independent groups)

Who is our example of a cross sectional study?

Becker (comparing disordered eating behaviours in two separate groups of 17 year old girls, one from 1995 and one from 1998)

What are some issues with cross sectional studies?

- Cannot control for individual differences

- Cannot determine progress (one group may just be better, not that they have made more progress)

What are some strengths of longitudinal?

- Controls for individual differences (cross sectional do not do this)

- In clinical it is advantageous as it can track the progression of diseases such as S1 and the success of treatments such as CBT over time