Alternative methods: 2 - Single case design

INSTRUCTOR: Single-case design.

This is probably one of the most common types of quasi-experimental designs,

and sometimes it gets a little confused with case studies for obvious reasons.

It includes single case design.

It sounds like a case study.

But unlike a case study,

so case studies usually just describe people.

There's no real manipulation or experiment going on,

there's no exposure to some type of stimulus,

and then to measure a reaction.

So with an actual case study,

you're just following them in their life,

seeing how they react normally to things,

and describing that very special case.

With a single-case design,

again, this is quasi-experimental,

you are looking at manipulating them in some way oftentimes.

How does someone with depression react to this type of therapy?

Or how does a pack-a-day smoker react to this type of medication or treatment?

Again, you are running a type of experiment, it's a quasi-experiment.

You're not just following these people around and recording their everyday lives,

you're trying to change them in some way,

usually, or treat them is maybe a better way of saying it.

Also, single case, and this is where I don't like the way this is named—

it's misleading—it implies that you're following one person.

That's really never the case with a single-case design.

The reason why we do call it a single-case design is because

we're usually analyzing data on an individual basis.

Pretty much all the analyses that we've been doing so far have been on group levels.

Comparing group averages, seeing if there's

a correlation between two variables on average.

The difference with a single-case design is you're

measuring change in individuals over time.

You often hear things like two out of three people benefited from this therapy.

Well, that's a quasi-experimental single-case statement.

You're measuring things on an individual basis.

You're not saying, on average, people got 30% better,

you're saying two out of three people got better.

I'm going to talk about one of the most common types of

single-case designs which involves some type of pre-post measure.

Usually, you're measuring the DV at a baseline.

I'll go and put this up at a baseline period.

We call that baseline because it's before manipulation,

it's just the regular level.

Then after the manipulation,

usually what we call a treatment period,

because some type of treatment or effect has been undertaken.

A real classic one,

one that's received a lot of interest lately as

a possible treatment for depression is called deep brain stimulation.

This is like having a pacemaker attached to your brain.

In a real way, it really is like that.

You have a pacemaker battery-like device implanted behind your collarbone,

and then electrodes go into very deep centers of your brain,

especially in the limbic system where depression is thought to originate.

These deep brain stimulations actually shut down

or calm down areas of the brain that might be involved with depression.

In 2005, this was a very experimental manipulation.

This had previously only been done with lab rats and some types of monkeys.

What they did, they wanted to test it on sick,

severely depressed patients, which is

what we often do with new medications or treatments.

We pick those people who,

for lack of a better term, have nothing to lose.

They're at the bottom of the barrel.

Really, they could use any type of possible treatment.

Basically, beforehand, they took measures of the depression as using

themselves as a comparison group to see if

they get better over time with this new type of treatment.

Then, of course, they undergo the surgery necessary to

implant this deep brain stimulation device.

Again, we're looking at individual changes in depression, not group-level changes.

That's part of the single-case design.

With some of the individuals, they found that it really

made not much of a difference or no significant difference.

Maybe they only went down a depression score,

maybe from eight to seven on a one to ten depression score,

whereas other people showed really dramatic decreases in depression,

in some cases alleviating depression all the way.

Again, we're looking at this in an individual basis.

Each line represents a different person.

In the end, the data looks something like this with

basically two people showing negligible benefits or non-significant benefits,

thankfully not getting any worse,

but no real change and four of the six showing good benefits and in some cases,

even complete alleviation from depression,

which is, of course, what you'd want to see.

Again, that's looking at an individual basis here.

It's a quasi-experiment because there was no control group.

A true control group in this case,

and it would be unethical which is just why it wasn't done,

would be to have people undergo surgery to implant this device, which is, of course,

very risky, and then basically to

think the device is on but to never actually turn it on.

In this case, that's just too much to ask for a control group.

Again, depression is a very detrimental thing.

These are people who are severely depressed,

so it would be unethical to withhold treatment from them.

But then without this control group,

there's lots of confounds that may have

alleviated depression for these four out of the six individuals.

The biggest one being a placebo effect.

Lots and lots of studies show that when people think they're being treated,

oftentimes, their symptoms will be lessened.

This can be anything from an actual treatment to just a sugar pill or a placebo pill.

Even with no treatment whatsoever,

just the thought of being treated can oftentimes help people that mind over matter,

especially with mental illness.

If someone thinks they're being treated, they might think, well,

I think I'm less depressed than I was before,

but they're just thinking more optimistically.

Another confound, and this is especially prevalent with research on the mentally

ill is that lots of people with

mental illness actually get over their mental illness on their own.

This is something that we therapists don't talk about a lot because, of course,

we like to tout that therapy and medication are really good things, which they are.

They do help people oftentimes get over mental illness sooner than they would otherwise.

But typically, about 60% of people with

mental illness do get over it completely on their own.

This includes anything from depression,

usually not severe things like schizophrenia or bipolar,

but depression, lots of mood disorders included.

Now, this is unlikely in this group,

though, especially at a 60% level,

because they selected people with severe and prolonged depression,

people who have had it for years, were previously untreatable.

It is unlikely that these individuals would just snap out of

it in the first initial weeks of this treatment.

Again, I don't think this is such a problem in

this study because these were very severe patients.

But sometimes just getting a baseline measure of mental illness

can help people motivate themselves to make changes in their life to get better.

Especially for people with maybe mild to moderate depression,

taking a depression inventory where they're listing

all the things that's been wrong with them so obviously,

depressed mood, maybe insomnia,

not eating enough, isolation from friends and family.

People might take that as a wake-up call and go,

wow, I really need to eat more,

and I need to rest more,

and I need to contact my friends and family and actually

can help them to snap themselves out of that depression.

Again, I don't think this is a problem here because these were,

again, very severely depressed patients.

Probably is a case that this wouldn't play that big of a role.

But one way to deal with these confounds,

is to do what's called a reversal design.

It's basically if you see an effect, which they did here,

four out of six patients showed positive results,

basically alleviations in their depression scores,

then you might want to,

in essence, take away the manipulation,

take away the treatment, and see if they return back to their baseline scores,

see if those four out of six return back to depressed scores.

Now, this is called an ABA design.

In this case, A really just means what's happening before their baseline and B,

what happens after their treatment condition.

ABA, going from baseline to treatment,

and then hopefully back to baseline once you remove the treatment.

They did this with one of the individuals.

Whether or not this is ethical,

this is a gray area,

but at this point, this is one of the only ways to

really rule out things like placebo effect.

With one of the individuals who was showing

a very positive result from the deep brain stimulation, they basically,

because these people got a week-by-week checkup,

where they fine-tuned the pacemaker inside them and all that,

with this individual, they basically turned it off without telling him.

Low and behold, within a couple of weeks,

the patient returned back to baseline.

This is a good indication

that this is the actual treatment that's doing it and not just a placebo effect,

because for all this person knows,

they're still receiving treatment,

so it rules out things like placebo effect,

but also things like just self-recovery from depression.

Of course, this is maybe unethical,

because now you're withholding treatment for someone who really benefits from it.

What most often they do with these types of designs is not just an ABA design,

but an ABAB design.

If they find that a person does return back to baseline,

they again instill the treatment as soon as they start showing symptoms back to baseline.

Hopefully, so that this individual doesn't

have to suffer for any prolonged amount of time.

In this case, again, they did this.

They restarted the deep brain stimulation,

again, without this person's knowledge,

and within even a shorter period of time,

a few days, he returned back to his treatment levels.

This is even better for the whole anti-placebo argument because,

again, this is without his knowledge.

It's being turned on and off.

This is a replication of the effect multiple times in the same individual.

Really good indication that it really is the deep brain stimulation and not something

else just random changes in the person

over time or placebo effect causing this difference.

[NOISE] Just some characteristics of the single-case design and

a good way to differentiate it from regular types of experiments.

For one, of course,

it examines people individually as opposed to a group,

so it's not going to talk about things like group averages.

It's going to be saying more like four out of six people, for instance,

in this case, did show significant improvement in their depression scores.

Most of them do employ this reversal of design so

either an ABA or an ABAB design.

Of course, what makes it a quasi-experiment is,

well, in this case, very clearly,

there was no control group.

Without a control group, you necessarily can't have

experimental control or randomization because those require multiple groups.

But even with multiple groups,

usually with a quasi-experiment,

you don't have any type of true control over

what patients are experiencing other than the independent variable or the treatment,

and there's no random assignment,

because usually, you're dealing with person factors like depression.

Most often these things are used to test the effectiveness of treatments.

They're very common in therapeutic designs,

especially involved with medications.