Do Network Centrality Predict Overall Depression Symptom Reduction With Lifting of Social Distancing Protocols?

Hypotheses (Hs) H1: In the cross-sectional depression-metacognitive network at T1, the
symptoms depressed mood, little interest/pleasure, and self-blame and the metacognitive
coping variables rumination/worry, threat monitoring, situational avoidance, thought
suppression, and uncontrollability of thoughts will be the most central variables.

H2: Reductions of the most central variables of the cross-sectional network from T1 to T2
will be more related to overall reduction of symptoms in the same time frame than reductions
of the less central variables.

Study design and participants The design is a longitudinal observational survey of the
general adult Norwegian population during the COVID-19 pandemic. Eligible participants are
all individuals of 18 years and above, who are living in Norway and thus experience identical
distancing protocols, and who provide informed consent to participate in the study. For this
study, only participants reaching the cut-off value (>= 5; Kroenke et al, 2001) for
subclinical symptoms on the PHQ-9 at T1 will be included, amounting to 6 508 individuals. The
strict social distancing protocols were implemented in Norway at March 12. 2020 and the first
data collection in this period (T1) has already been done. It lasted seven days and was
between March 31st 2020 and April 7th 2020. Thus, the strict protocols had been held constant
during the two weeks prior to data collection, as well as during the data collection week.
Furthermore, no new information was given by the government during this period with regard to
changes of distancing protocols, keeping expectation effects constant. From June 15., the
majority of the distancing protocols will be lifted in Norway, and the T2 period is defined
from this date. Data are set to be collected from the sample providing data in the first
collection (N = 10 084), starting one week after the lifting of the protocols, that is, from
22th of June. The collection will last until enough data has been collected, but no longer
than three weeks.

Ethical approval of the study was granted by The Regional Committee for Medical and Health
Research Ethics and the Norwegian Centre for Research Data (reference numbers: 125510 and
802810, respectively, for the first data collection, and , respectively for the second data
collection), where the study protocol and analysis plan was approved prior to data
collection. The study is conducted in accordance with the guidelines of the Strengthening the
Reporting of Observational Studies in Epidemiology statement (STROBE; Von Elm et al., 2007).
The pre-registered protocol for a study of loneliness based on the first (T1) data collection
can be found at Clinicaltrials.gov (Identifier: NCT04365881). The study is part of The
Norwegian COVID-19, Mental Health and Adherence Project (Ebrahimi, Hoffart, & Johnson, 2020).

Procedures The survey is disseminated online. At T1, it was disseminated in a systematic
manner to give the adult population an equal opportunity to participate in the study. The
dissemination procedure involved information about the survey through broadcasting on
national, regional, and local news channels and provision of the online survey to a random
selection of Norwegian adults on Facebook. The dissemination procedure is described in detail
elsewhere (Ebrahimi et al., 2020).

The stopping rule for the first data collection was designed to ensure that the SDPs were
held constant for two weeks prior to and the week during the data collection period, as well
as controlling for expectation effects by stopping data collection instantly once information
concerning forthcoming modification of the social distancing protocols were given. The second
data collection - approaching the 10 084 individuals of the first collection - will start one
week after the strict protocols are lifted (June 22.) and last three weeks.

Sample size and power The sample providing data at T1 comprised 10 084 participants,
ascertaining power for the questions asked. All these participants will be invited to partake
in the second data collection during the lifted prptocols period (T2) in accordance with the
study plan. The mentioned 'Norwegian COVID-19, Mental Health and Adherence Project' involves
multiple studies, where some involve a Complex Systems (Network analysis) approach. These
mutlivariate analyses require large samples and power analysis was conducted accordingly.
Following power analysis guidelines by Fried & Cramer (2017), it is recommended that the
number of participants be at the very least three times larger than the number of estimated
parameters. However, more conservative recommendations by Roscoe (1975) for multivariate
research, recommends sample size that is ten times larger than the number of estimated
parameters. For our network of 9 PHQ-9 variables and 16 CAS-1 variables, the number of edges
in the network is 25*24/2 = 300. Thus, according to the conservative advice of Roscoe, the
required sample size is 3 000.

Blinding No blinding is involved in this study.

Is there any additional blinding in this study? Not applicable

Randomization No randomization.

Sampling Plan

Existing Data Registration prior to the analysis of the T1 data and prior to the collection
of the T2 data.

Explanation of existing data The pandemics (and the consequent social distancing protocols)
occurred, by its very nature, unexpectedly and the project could not be planned in advance.
Thus, the first data collection started immediately and before pre-registration. It started
during the time-period with the strictest protocols in Norway, and the first data collection
was stopped before these protocols were modified or new information about them were added. We
have avoided any network analysis of the data.

Manipulated variables Not applicable/NA

Statistical analysis To test H1, the network of the 9 PHQ items and the 16 CAS-1 items will
be estimated using the R package qgraph (Epskamp et al., 2012) in a random half of the
sample. Network stability tests will be conducted using R package bootnet (Epskamp, et al.,
2018). An undirected partial correlation network will be estimated, resulting in associations
between each pair of symptoms controlling for all other associations among symptoms.
Centrality indices - strength and betweenness - will be computed according to the method of
Robinaugh et al. (2016). Strength refers to how strongly a node relates to other nodes.
Betweenness refers to how important a node is in paths between other nodes. Hypothesis 2 will
be tested in the other random half of the sample. The outcomes of interest will be the degree
to which change in a variable from T1 to T2 correlates with the change in the PHQ-9 total
score (minus the variable examined if it is a symptom).

Missing data There are no missing data in the first data collection because the survey
includes only mandatory responses. Dropout from the second data collection is to be expected,
but the amount of missing data is uncertain. The multiple imputation procedure in SPSS will
be used to impute missing data.

Exploratory analysis We may do other exploratory analysis that we have not yet thought of at
the time of preregistration. If we do such exploratory analyses, we will explicitly state
them as exploratory in the published manuscript following common publishing guidelines.

Other The data include one directly identifiable variable (contact information) for
participants in accordance to the General Data Protection Regulation (GDPR) law in EU, which
is to give the participants the opportunity to have their data deleted upon request. Data are
thus kept on a safe server belonging to the University of Oslo and will be accessed first
following de-identification.